Language reccommendations?

I must say, I am damn good with taking on new languages. I have no doubt that I couldn't learn any language. I'm a native English speaker, with 2 years of French, and going onto my 3/4 years of Chinese (Mandarin). I want to learn something else.... something i'd actually use fairly often. For example, I love Swedish and Russian, but I've yet to come across a Swede or Russian who didn't speak english. In Connecticut, you find a lot of Polaks and Spanish (mostly puerto ricans) people. So those two would be useful for sure. Thanks for the advice :)