Just google the city. A lot of places here just have a class in a fitness studio somewhere with a purple belt level guy that teaches three times a week. You can probably find a place like that in every major city.
Also... luta livre is big(er) in germany. You may just end up having to do that (as I did) to pass the time during your stay. It's like sloppy no gi jiu jitsu with more leg locks.
As the poster above me said.. when you get into the LARGE cities, you'll find an alliance or gracie barra gym (Frankfurt, Duesseldorf, Berlin etc.)
Good luck,