We will be in Provence for 3 days in late Sept. and would like to see Aix and St. Remy. Does anyone know if there are buses or trains to these places from/close to the Marseilles airport? Also, where to stay if we don't have a car?

There is a bus directly to Aix from the Marseille airport. You would get off at the Gare Routiere (bus station) in Aix and not the Aix TGV station which is outside of the city. Here are the departure times :

05h25 - 05h55 - 06h25 - 06h55 - 07h25 - 07h55 - 08h25 - 08h55 - 09h25 - 09h55
10h25 - 10h55 - 11h25 - 11h55 - 12h25 - 12h55 - 13h25 - 13h55 - 14h25 - 14h55
15h25 - 15h55 - 16h25 - 16h55 - 17h25 - 17h55 - 18h25 - 18h55 - 19h25 - 19h55
20h25 - 20h55 - 21h25 - 21h55 - 22h25 - 22h55 - 23h35

How long does this trip take? Is it less expensive to take the bus then the train?

The bus takes 30 minutes and cost 7.50 euros. I dont know how much the train costs but you would have to take a bus from the airport to the train station in Marseille and then catch the train so it would take much longer I would expect.

Thanks, Morgan, for the bus schedule. Do you know if there are busses to St. Remy as well?

Not that I am aware of. I think you would have to take a bus into the train station in Marseille and then switch to a train. Here is where I got the bus info : http://www.mrsairport.com/eng/index.jsp

Click on access to find info about buses etc.