I don't know about the schools you mentioned but Alliance Francaise in Montpellier is the worst language school I've ever been to - large classes, poor organisation, and very inexperienced teachers.

I lived in Montpellier for 6 months or so and while the old town is pretty, the weather's great, and it's relatively cheap, I don't think it's a nice place to live.

There are a LOT of homeless people, especially young people, in the streets. The level of theft and burglaries are very high and consequently you home insurance will be high, higher than Paris. Montpellier is 10km from the beach and the beaches are crap. I also found it to be quite remote if you want to travel.

Oh and don't forget they speak with a very strong accent making it a little more difficult to learn the language, imo. Although I must admit I quite like their accent.