you can do that! I've done it before. But AP room rates aren't as predictable as before or plentiful. I usually book
AAA at the hotel where that rate is comfortable for me. (i,.e. Maybe on AP I'd stay at Contemporary but at AAA rate I book CB or WL as I know I can afford them on AAA rate) Anyway, if/when AP rates become available for my stay I call right away. I then try to get AP at the hotel of my choice (Contemp) or use it at CB or WL. In truth, you're not really applying it to your existing reservation ... there has to be a room available at the AP rate that you can book....and then they cancel your orig. AAA rate ressie.
That's why many people feel you shouldn't book a room (AAA or rack rate) at a hotel you hope to eventually snag an AP rate for. If Disney feels occupancy is at a high enough level, they don't offer many rooms at that hotel at the AP rate. So by booking early, you just might not get an AP rate at the hotel. On the other hand, I'm not willing to chance not having a nice room at a rate I can afford....so I still book AAA someplace nice...and then hope for the best.
SOrry for the lengthy answer, hope it makes sense.
