The AP discounts generally apply to Downtown Disney restaurants and the ones at Swan/Dolphin. They seldom have any AP meal discounts for park restaurants.
Actually, I believe that there is currently a 10% discount at most of the Epcot full service restaurants for lunch Mon-Fri. Besides Downtown Disney, the Sandtrap, Kona and Grand Floridian Cafe offer them for lunch, too. Have you checked Mousesavers? Have your passholder sleeve with you, though. We asked for the discount at GFC a year ago or so and our waitress said they only had a AAA discount. We happened to have that card along, too, but I checked the sleeve later and sure enough it was listed.