I think this article is interesting, but probably not scientifically valid.

I was in France for 10 days in 2004, and didn't speak but a few words of the language- but everyone was very nice! I actually didn't run into anyone who was rude, but also did make sure to at least give basic salutations in French. (I also had a friend who spoke French, but even when I was out alone I found people very helpful despite my language deficit).