I have gotten cabanas both visits. I think because you are going during a quieter time your chances are quite good. We have gone during Presidents week which is a busy time and not only gotten Cabanas, but ground floor and the Cabana we wanted both times (8A).
If there is a convention, they do tie up one Cabana building and alot of Casitas, and Casitas is the most requested from what I've read.
May not get all the requests, but you have a good chance of getting the area you want.
If you get there and they have given you something else, ask again.