I made a short attempt at learning mandarin a few years back, but I've put that on hold for a while. My favorite phrase is "Wo bu da hwei sho niminde hwa." My wife says I deliver it very well.

There are chinese student clubs at most major universities. These guys often like to practice their English. Also, I suspect there might be clubs at some very few american / brit high schools where students might be learning mandarin. You might check out the web for references.