Lauren I would definitely take the train to Aix and Avignon. I was in that area in 2008 at about the same time of year and it was luscious! Aix will be in full lavender bloom and Avignon is your cheesiest dream ever.
Kaue I do recommend Cinque Terra, specially if you enjoy hiking for the best is to go from one village to the other.
I have fancied visiting the French Riviera, specially Marseille and Nice, but haven't managed it yet.