We did this in 2004. We tried "downsizing" and booked POR. We checked in, our room was ready, we left our luggage in our room and headed over to MK. Well Dh wasn't happy with the room, the bus was standing room only, and when we got off at MK and DH watched the boat coming over from GF and Poly he decided that was it! The kids and I went into MK and DH set out on his mission. His plan was to go to GF, Poly, CR or WL (in that order) in hopes that we would be able to switch.
We had no problem switching to the GF, and in fact since we already had the AP rate for POR, they gave us the AP rate for the GF.