Gustavo was an excellent host and the place was in a central area.
We arrived to Berlin by train and Gustavo told us before hand which trains we should take from there to his place. The train station near his place is Bahnhof Zoologischer Garten. If you prefer to walk it is quite near (less then 10 minutes) and you cross one of the iconic churches which wasn't completely destroyed in the 2nd world war (Kaiser Wilhelm Gedächtniskirche).
The house had everything you need if you want to cook at home and to keep a balance between going to a restaurant and spending less money with food from the supermarket. Talking about the supermarket, there is one quite nearby the house in the same city block, near Wittenbergplatz (good place also to catch both bus and metro). We also watch some of the European UEFA Cup at home; we were just sorry not to watch Germany playing because we needed to go back home. Otherwise we would have went outside and mingle with the Germans! :-)
About the public transports, you have the bus 100 right in front of the house, which takes you to important places, but has described before you have nearby a lot of options.