I've participated in a number of postings about traveling in Provence by bus. I arrived in Aix on March 1, went to Arles and have been in Avignon and will end my two weeks stay here on Sunday.
No problems utilizing bus and train systems in the first two cities. Avignon has been a challenge! I can assure you that I double check, triple check and still have been perplexed by travel out of Avignon. And even checking with the agent the bus station doesn't help, and even though they speak English something gets lost in the translation.
Certain bus lines only run in July and August. Certain bus lines require a phone reservation 24 hours in advance or if a Monday departure, a Friday reservation. The bus agent in Avignon spent 45 minutes with the reservation agent attempting to get me a reservation for the bus trip. No way I could have called and made that reservation!
There were also certain towns that I could get to but would be unable to return that same day to Avignon. Very disappointing that the online schedule was not as accurate as I was hoping it would be as I am a meticulous planner. Just FYI out of summer season travelers.