Don't have any personal experience with the school, but I'd jump at the chance to study French (or anything else) in Montpellier. It's definitely a university town - lots of young people, plenty of stuff to do.

You're always going to have the issue of people "practicing" their English on you. What you can do is offer to do some "bi-lingual" conversation groups - 45 minutes in French, then 45 in English over coffee or a glass of something or a light snack. Should make you immensely popular.
Cheers,
Bev