In the Czech Republic, I had a couple of occasions when there was an obvious language barrier and the question "Sprechen Sie Deutsch?" was put to me. In Poland, I wouldn't exactly go around greeting people in German, though :-).

German and French are good back-up languages. I have heard -- but not personally confirmed -- that Russian can provoke hostile responses from some Eastern Europeans. English is a nice, safe, neutral language especially in Central and Eastern Europe and more and more of the younger generation are learning it.