Access to the city. The Tallinn Airport is small, cozy and well-organized — just as the rest of the country (most of the time). The city centre is easily accessible by tram No 4. If you want to use this option, you can buy a ticket (2€) from the driver, or, if you intend to use public transport more often, see instructions below (Public transport). The conference hotel, Park Inn Central, is about 100 m from the Hobujaama tram stop. You should move backwards from the direction the tram is taking and note a turn into an alley, where the entrance of the hotel is located. 
Alternatively, you could also take a taxi. The official taxis of the airport (available at the stand right next to the door) would cost about 10-13€ to the hotel. Alternatively, you can order a taxi (again, see the Public transport section).

Venues. The Park Inn Central hotel is conveniently located more or less exactly between the university and the Old City, both of which are accessible on foot — about 10 minutes of leisurely walking. If you are using the tram, the university is one stop away from Hobujaama (you should take tram 1 or 3 going toward Kadriorg). All the venues of the conference are in the Mare building, there will be signs guiding you from the main entrance. You should pass by the old building and head for the new and bigger one called Astra.

Eating. During the conference, the university cafes provide affordable student-style lunch. The cafe called Oaas (“Oasis”) has a special vegetarian section; things may be a bit more complicated for vegans. There are also several restaurants in the vicinity of the university. Villa Thai (Vilmsi 6, +372 6419347) offers Thai and Indian food, somewhat tuned down to match Estonian tastes, Nop (Köleri 1, +372 6032270) is popular for lighter, eco-friendly and multicultural health options. A small walk away in the direction of the Kadriorg park, you find solid Estonian-Mexican food in Cantina Carramba (Weizenbergi 20a, +372 6013431) and possibly the best range of coffees with a nice lunch menu at Gourmet Coffee (Koidula 13a, +372 6613035). A visit to any of these would be feasible during the generously timed lunch breaks.
For dinner, the right decision would be to head for the Old City, and there is a lot to offer for a wide range of taste preferences. But as this is a popular tourist destination, you might want to ask a local for advice, as there are also quite a few tourist traps. Some of the best culinary experiences are to be found a bit off the beaten track. A high-end Japanese restaurant called Haku (Lätte 6, +372 56314547) takes pride in its authenticity, and charges accordingly. Another high-end Asian restaurant is Chedi (Sulevimägi 1, +372 6461676), with mostly Chinese-based culinary creations on offer (try the Pi Pa duch and honey pork with sesame). For European-style restaurant food, good options are Pegasus (Harju 1, +372 6623013), with spectacular views of the Niguliste church from some tables (try the duck breast), as well as the kitchen-sharing Rataskaevu 16 (address as in name, +372 6424025) and Väike-Rataskaevu (Niguliste 6, +372 6011311). You might want to try the wild boar neck or braised elk. 
For more local flavour, Vanaema juures (The Grandmother’s Place, Rataskaevu 10, +372 6269080) offers you what a typical Estonian grandmother would. The restaurant is located in a cellar, however, so if you need to have windows wherever you are, you might opt for something more cosmopolitan during this trip. For a wide range of vegetarian food, Aed (Garden, Rataskaevu 8, +372 58593839) is your choice. 
If you really want to have a spectacular view of the Old City with your food and do not mind paying for it, the place to go is the restaurant on the top floor of the Fotografiska museum in the Telliskivi creative area. But you might as well enjoy an aperitif there and go to eat in one of the nearby eateries, such as Lendav Taldrik (The Flying Saucer, Indian, +372 6214222) or Frenchy (+372 56048262, too bad May is not oyster season).
Finally, there is a place where tourists normally do not end up. It has no signs on the door and no indication whatsoever that there is a place to eat and drink behind it. It is called NoKu and the address is Pikk 5. A blue, slightly worn door with a red frame. And a number pad next to it. Push 2580 and the door opens, go up the stairs and find the place where mostly artistic and intellectual types are often headed after hours. Budget-friendly, at least as far as the Old City hangouts go. The place will most probably be packed on a Friday evening though.

Public transport. Most of the places you need to go to are accessible on foot from the conference hotel, but if you are staying elsewhere or need to use the public transport a lot, you 
might want to buy a green public transport card (2€) at an R-Kiosk. There is one already at the airport, to the right of the exit to the city. At the Kiosk, you can load it with money and when you board a tram, a bus or a trolleybus, you touch a sensor and it deduces the fare (1.50€) from the card, telling you the balance. So when you use the card for the 4th time, you are breaking even. However, when you leave the country, you can sell the card back to the kiosk (or so we are told…)
If you prefer to move around by taxi, you should never flag down a car or take one standing idly on the street. Taxi fares in Estonia are not regulated and there are drivers who take advantage of foreign tourists, making them pay (legally!) as much as 50€ for just starting the trip. The safest way to use taxis is to download an app called Bolt (this Estonian company also works in many other countries). You need to type your destination in the app and it notices where you are. The slight inconvenience with Bolt is that, for example, in many places of the Old City traffic regulations do not allow cars not belonging to local inhabitants to enter or park, and Bolt sends your car to the accessible location closest to you, which you need to be able to find. The app can connect you to the driver, but their linguistic competences may vary. You do not have the same problem though, when going, for example, to the Mare building of the university (Uus-Sadama 5) or the Telliskivi creative area. 

Sights. We are sorry the conference schedule does not leave you too much time for these. You will most probably be wandering through the Old City and not miss the Town Hall Square and the nearby maze of streets with medieval architecture, and you might also want to climb up the Dome Hill (Toompea), to see the Parliament and the Dome Church with coats-of-arms of Estonian/Baltic German aristocracy on its walls. Opposite the Parliament, there is also a remarkable example of imperial orthodox kitsch called the Alexander Nevsky cathedral, commissioned by the Russian czars to assert their presence in the Estonian capital at the end of the 19th century. A place much more worth a visit is the Niguliste Church with the magnificent serial Death Dance painting. If you only go to one museum during your visit, it might be this one, or KuMu in the Kadriorg museum area, another 10 minutes from the university in the opposite direction — a fantastic piece of architecture carved into the rock, with good Estonian and international exhibitions constantly on display. Or, alternatively, the already mentioned Fotografiska, one of the few filials of the legendary Swedish photography museum in the Telliskivi creative area. This area is indeed another nice destination, a rebuilt old industrial territory with a lot of creative industries, eateries, small indie shops and so on, behind the railway station, walkable from the Old City and easily accessible from Hobujaama by trams 1 and 2, Telliskivi stop.
Even if you stay for a day more than the conference, you most probably won’t be able to see more than the things just listed, but if you do, then there is the Pirita (St.Brigitta) area with monastery ruins and nice walks along the sea coast through the pine forest, and the Memorial to the Victims of Communist Repressions in Maarjamäe, on the road — a remarkably modern, dignified and somehow light way to deal with collective grief. The nearby historical museum is obviously also worth a visit, as are so many other sites that you will nonetheless not be able to fit into your schedule this time.