that's a broad question, but here's my 2 cents:
-english-speaking will be just as bad everywhere...
-Nice and Marseille have real good weather. and beaches. Rennes and Lille have rain.
- as far as skate scenes, Marseille is the more established one. It's also a way bigger city.
-Rennes has a lot of students and is supposedly a big party town
personnaly I'd say go to Marseille, and the surrounding area. there's a lot of other interesting cities close by (Toulon, Montpellier etc)