We have stayed at the CBR two years in a row and loved the resort both times. In 2006, we were assigned to Jamaica Building 41. The walk to the bus stop and quiet pool was super short. The walk to Old Port Royale was short also. We loved the location so much that we requested it again for our 2007 stay.
This past visit, they gave us a free upgrade to Martinique. In all honesty, I wouldn't pay the extra money for the "preferred" location. The walk was about the same as when we were in Jamaica.
The buses were great no matter which location we stayed in. It all depends on what time of day you're catching the bus on whether or not you'll be required to stand. Many times, we had seats but would give them up if older people or young mothers with children were going to stand. The CBR is so centrally located that it doesn't take long to reach any Disney destination.