They had a special offer for AP holders last year-I don't remember the rate. It was on mousesavers. I called to book a room for a friend and they didn't have DC discount, Birnbaum or AP available-I called back later in the day and they had the Birnbaum offer available-25%. They knew the code for the AP discount-all I did was mention it. They didn't even have an ocean view room available for May and 10 minutes later they did.
You really have to check periodically-it changes all the time.
Keep an eye on mousesavers.com
If you already have a discount, I would say stick with it because they sometimes are hard to get dependin on when you are going.