South of France after London?

Hi all!
My bf and I a (26 year olds) are thinking of flying to Nice for a long weekend after we spend 4 days in London.

I've been to Paris and know pretty much everyone speaks English, but is it the same in the South of France?
My other question is, we'll be going in August and I know that's when the French take their holiday. Is it worth going? Will things be open?

If anyone has any recs of what to do in the South of France or where to stay- please let me know. TIA!