which month has better weather and costs and what areas
are most interesting
August is vacation month for most French,, so the south ,, especially near the coasts, will be VERY busy in august.Many places will already be booked up. Once the kids are back in school ,, it will be alot better,, but still nice weather . I would choose September.
September will be cheaper, likely be slightly less hot, and less crowded. Definitely go in September if you have the option.
Get the Michelin guide books for Provence and Languedoc-Roussillon and do your research to find the areas that interest you. I agree that Sept would be better.
william, I agree with the others that September would be a better choice. The weather should still be good, but perhaps not quite as hot. That's the fall "shoulder season" so I doubt there will be much (if any) difference in costs. Happy travels!