Casitas 4 and 5 are not preferred buildings and are close to the casitas bus stop (stop #2, but the first picked up and dropped off when going to/from the parks). They are not far from the main building.
Cabanas 9B is the closest cabana building, but it is now business class (starting January 1). The other cabanas are not far from the main building - 9A would be the next closest.
Most of the buildings at CSR are near a bus stop.