Am I correct that you are debating between Casitas 4 and 5? I guess if I had to choose, I'd pick Casitas 4. That's the building I've decided to request next time. (We were in 3 this time.) I think 4 is right by the Quiet pool, which is really pretty. Also close to Bus Stop #2 which is the first to get picked up. We were on the first floor this time, which is nice because you don't have stairs, but some people don't like being on the ground floor--didn't bother us!
You'll be fine in either building! Enjoy your trip!