Disney provides transportation within Disney property only.
You will need to go with an outside service (Mears shuttle, limo, rental car, taxi, etc.) to get from the airport to your resort.
I have never rented a car--to me, driving is stressful, and I don't need that on vacation. Others are stressed while waiting for a bus. You know your personality.
One caveat--the busses to Downtown Disney are very slow. Waits of 30+ minutes are common. I think this is mostly true in the evening. So, try DD during the day, or if clubbing is in your plans, prepare yourself for long waits. (or rent a car, or get a taxi)