I have the impression that Berlin is probably the most English language-friendly city in Germany. I've never been asked if I want a menu in English or German in any other place. And one can hear English being spoken on the street a lot.

More anecdotes: I know several people in Munich that don't have much trouble managing only with English - doctors, banks, landlords, travelling etc. I also know people doing the same in cities 10x smaller than Munich, but there it's quite tougher and the odds are higher that you'll have negative experiences.

I think knowing German is a big advantage in any of those cities. And depending on luck one can have pleasant or also quite unpleasant experiences when interacting with the locals in English.