Also factor in the time you're going to be spending learning Dutch. You'll probably get by with English alone since everyone will speak it with you, but it's certainly less than optimal.
Apart from London Amsterdam is probably the city where you can get by most easily speaking only English. It will be hard to fully integrate into Dutch social life without learning proper Dutch of course, but professionally it will not be much of a problem and the expat community is so large that it is fairly easy to build a decent social life within it.
You can get by perfectly speaking only English in most of Northern Europe.
Southern Europe is a different story.