We will be arriving on a Saturday around 1:30 p.m. and will be staying at CSR.
Does the DME for CSR share a bus with other resorts?
Approximately how much time should it take from the time our plane lands until we reach CSR? We are trying to plan out our first 1/2 day there and make a few FPP reservations.
Thanks! 
DME always (almost always, I guess there is a chance there could be a solo trip) makes stops at multiple resorts. In my past experience, CBR is typically one of the first to get let off though. Unfortunately, there is no real set pattern of drop offs, I am told they will adjust based on the number of guests going to a particular resort and what the need is at that time.
You will get varying times from other people I am sure, but I do not make any plans to be anywhere before 3 hours after my flight lands. It is almost always at least an hour to get to your resort from the time your plane lands, plus you should plan an hour to get to your reservation or fastpass. That gives a solid hour of wiggle room for things to happen. Again, just what I do. I am sure you will get other answers as well.
A general rule of thumb is to count on two hours minimum from wheels down to arrival at your resort. On my most recent trip, it was an hour and 20 minutes; on my last, nearly 3 hrs because of weather and a Disney Race. I’ve yet to be on a bus that is heading for only one resort; they all seem to share.