It's definitely easier if you speak the language. Koreans don't really hold your hand and tend to bombard you with long, fast-spoken sentences even if you try to explain that you don't speak the language :p At the same time it's very easy to make friends that don't mind giving their broken english a try in order to make a conversation with you.

I am not fluent in Korean (still very far from becoming) but still consider Seoul as one of my favorite cities (if not my favorite) period