I've got friends who've been to Warsaw (similar to Krakow apparently), and they said it was a great place to visit. I've passed through it, but that was on a bus journey from Lithuania to the Czech Republic. Unfortunately the bus didn't stop in Warsaw, only went through it on to the destination. Wish I'd stopped off there now
I've a Polish friend who comes from a town near Krakow and she says Krakow is a fun place! But other than that I can't say anything more about the place...
Oh, apparently the younger Poles speak good English now so you shouldn't have too many problems communicating. Most former Eastern Bloc countries speak German too, so if you can speak that you'll get along fine (helped me out tremendously in the Czech Republic). Whatever you do, DON'T speak Russian as the Russians are hated...