I faxed a request but also had it on my reservation. I actually faxed it once at 7 days before and again at 4 days before.An old Disney pro swears by this method.
Don't know if it will work but a friend of mine who has visited Disney resorts 17 times and always makes requests right down to the room number he wants has never been disappointed. Now his family usually stay at the Yacht Club , so I don't know if that makes a difference.
Leaving Thursday morning for 11 days at CBR so i'll let everyone know when I return if the fax mad a difference.