You can't buy AP or PAPs at the resorts. You'll need to get them at Guest Services, either at the parks or at DTD. We've gotten ours either in the mail or purchased them outright at the International Gateway at Epcot. Never seems to be any line there.
We want to convert our 7 day PH passes to AP this trip. I've heard that it's best to use one day and then convert. Not sure why. Can anyone confirm this? TIA!