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I just made a 1 night ressie for Sat. March 12 (night before we check into Wilderness Lodge for week) at Pop Century using AP discount rate. She told me that since I have to present my activated annual pass upon check-in, the only place to get it would be the theme parks. Since we are coming into Orlando at night, she said that if I didn't make it to Epcot by closing (this is the latest park that is open), that I would be charged the regular room rate as there is nowhere else to get an activated annual pass.
She was extremely knowledgeable and helpful (in fact, she is probably the best CM who I have ever spoken with), so I have no reason to doubt her, but according to AllEars & Mousesavers, several other places (Downtown Disney, airport stores, Character warehouses and Ocala center) also sell them, but she said that wasn't the case...