I don't know about AP rates but with FL rates my brother was able to make a reservation in the lobby but he had to call CRO. The front desk was not able to give him the discounted rate without getting the reservation done through CRO. The reservation has to be in advance. I guess even by minutes.
Having said that if you know you are going call and make reservations. You don't want to find out the resort you want doesn't have available AP discount rooms.
Good Luck,
Shirley