In Berlin, sure. The elder may not be able to understand your English.

Some rules of thumb:

1) The younger, the more likely to be able to speak English.

2) Rural area less likely to speak English (well) compared to big cities and tourist areas.

3) In IT/tech world in Germany you should have far less problems than say farmers.

I'd say those count in general though :) if you go to Amsterdam people are much more likely to speak English than a local, small Dutch town foreigners generally haven't heard about. And, English is very practical in our globalised world. Make no mistake about German though; it is also a practical language in Europe.

I don't speak German. In Berlin it's not a big problem, particularly in certain neighborhoods where even waiters at restaurants may not speak German.

English is taught in every school in Germany.

You should have it easy to get by.