I do speak fluent French, but as someone else said, you still have to learn the proper vocabulary for things like "upwind" and "base". I learned to ski in French, and I'm still not sure of the English for some things.
I flew at Mandelieu (near Cannes), with an instructor, mainly to get the hang of doing the radio in French and other quirks of flying in France. But it wasn't a huge success because Mandelieu (which is towered) is largely used by French pilots as a place to improve their English!
John