1. Do I need to let the front desk the time that I will be arriving or is the shuttle available all the time?.
2. Do you have available parking?
I would check with the front desk as far as a check in time to make sure the room is available. We had to wait for our room but it wasn't a big deal. They held our luggage behind the desk and we wandered around town.
There is a large parking lot. It was difficult for us to find with our GPS because of road construction. You have to go through a locked gate. Use the speaker on the side to press the button and talk to the front desk. I do not think they have a shuttle.
The hotel is very close to the central station in Avignon. You can walk in 3-5 mins. If you are coming from the TGV station, you can get the local train from the TGV station to the Avignon central station for a few euros. They run every 20-30 minutes (depending upon what time you are arriving).
Get an answer from Hotel Cloitre Saint Louis staff and past guests.