Relax, English is spoken at most of the larger airfields, basicly, if its got an ATC then they probably speak English - seem to remember they do at biscarrosse. The only time you should need to speak any french is at uncontrolled airfields when you declare your intentions in french. I usually call the airfield before I go there to know if someone will speak English there.
I also second what was said above. Im based in the Bordeaux area, and Everyone is really helpful down here, even when you are not really sure where you are supposed to be or what you are supposed to be doing. Just ask Info or ATC if you dont know something, one of the instructors at my club is a controller at Merignac, he has regularly told me not to worry, just ask, talk to someone!
The only thing I can add (though Im sure you're doing this anyway) is make sure you know about the Restricted areas and Entry/Exit/Joining proceedures for the Bordeaux area, Eg. Arcachon/Cazaux/Biscarrosse, there is definitely alot of military activity during the week, but even weekends the restricted areas are active. The good news is you can request a crossing anytime and they are usually very civilised and accomodating.
Oh, one more thing, lunch in France is between 12 midday and 2pm (sometimes 3pm, eating is serious business in France!), so you wont be able to get fuel at this time.
Regards, SD.