We did this area in September a couple of years ago. Strangely, a lot of stuff in Quebec and the Maritimes starts to close down right after Labor Day, despite the superb weather. Crowds were very light, and campgrounds usually under half full.
As far as language: a little pidgin French and a sense of humor worked 99% of the time. The 1% of locals who are putz's are the same 1% you find everywhere. We just ignore them and move on.
And oh yes: Quebec has some of the finest eating establishments on the continent!
