We never rent a car in Disney while we stay at the resorts. If we head down to Vero after, we will rent a car on the day we leave.
As for bus transportation at BCV, it is good. You catch the busses out front of BC. We waited approx 20 minutes each day we went to MK and AK. As for Epcot, we walked the whole whopping 10 minutes there, and took the boat to MGM. There is a walkway to MGM and I applaud you if you take it, lol, it is way too long for my taste.
On the boat ride home from MGM a week and a half ago, the boat driver was going Sooo slow, we all started wondering why, when all of a sudden, he stopped the boat and announced if we looked out the right side of the boat we could see the shuttle that was just launched. Pretty cool!