I know a lot of Polish people in New Jersey and New York. In Greenpoint, Bay Ridge etc. Yeah, they definately talk to each other in Polish a lot, even when other people are around.
There are a lot of Russians in the New York and New Jersey area, too. Brighton Beach is all Russians. They do the same thing, talking to each other in Russian but feeling left out if other people speak in a language they don't know.
I think it's an Eastern European thing. Thats cool, though. They mostly speak English pretty well, and they'll teach me curse words in Polish and Russian! That's fun!