Originally Posted by
HeartIsAching
Are you in the U.S., or France? If you're in the U.S., they'll likely speak English in order to be polite to you, and that's proper.
Funny story:
Years ago a friend of mine and I went out with two Chinese-American girls, who kept talking to each other in Cantonese and then laughing all evening. We'd asked them to stop as it was rude and they ignored us. Both of us spoke German at the time (I'd just gotten back from living there for 3.5 years, and he was reared there), so after the 3rd or 4th time the girls did that, we struck up a conversation in German. Should've seen the looks on their faces. Last time we went out with them. Duh.