I have been looking at some linguistic maps of France, like this one:
It seems there are local non-French languages everywhere, but I wanted to test that with a local person. Today I got my opportunity. I went for a haircut, armed with some basic haircut-related vocabulary: plus cour (shorter), derriere (back), avant (front), a cote (side). I managed to communicate what I wanted: number four back and sides, and shorter all over. Like every other hairdresser I have met, my hairdresser today was up for some conversation.