Berlin has been arguably the most international city in Germany for a long time. During my stay in Summer of 2017 I did hear a lot of (American) English, much more than in the nineties, chiefly in Prenzlberg and Mitte though. There was even a proper American greasy breakfast restaurant serving pancakes and bad coffee (Ok, I made the bad coffee part up). Every German learned some English in school (there was a Generation which learned Russian in the East instead though), but w/o sufficient practice, many aren't comfortable using it later in life. With landlords this will be hit or miss.