The workshop takes place at Freie Universität Berlin Habelschwerdter Allee 45 14195 Berlin Room JK 25 / 130 Map
The venue can easily be reached by public transport. The closest stop is U Dahlem-Dorf (lines U3, M11, X83). http://www.bvg.de/en/
Hampton by Hilton Berlin City West (It has a very good location within the city. Getting to the workshop takes about 30 minutes by public transport. Ask for a room to the back, so the window is not facing the train line.)
Hotel Steglitz International (This one is closer to the workshop, but a bit farther away from the airport and sights).
This site offers several apps for your stay in Berlin, e.g. using public transportation, offline city map, city guide.