I'm an advocate of renting a car. Provence is a lovely area with many small delights. I can't imagine trying to rely on local transport. A bus might be fine to get between towns, but there are many things to see and do that are not in towns proper. A car is the only realistic way to access them. I've traveled with my husband in Provence and also with a friend while staying at her home in Apt. It's not only the sights, it's also the restaurants which can be tucked away in the countryside. A car simplifies planning a day tremendously.