If you do decide to make your purchases at The Disney Storey or the airport, please be aware that what you are purchasing is only the certificate, necessitating a visit to Guest Relations at the parks or Downtown Disney to convert them into working tickets before they can be used. There is no monetary savings for advanced purchases of Annual Passes, so why make 2 stops?
As another person posted, you may purchase your APs at any of Disney's main theme parks, or at Downtown Disney. The water parks only sell the Premium Annual passes, as the Annual passes don't include those parks.
If you do go to Downtown Disney to purchase your AP's note that the Marketplace location had been moved to between Ghiridelli Chocolate and Team Mickey. The hours at that location are 8:30 am to 11 pm Sun through Thur, and until 11:30 pm on Fri and Sat. It is best to get there at least 15 minutes before closing, as it does take time to enter all of the demographics into the computer for each AP. The Westside location is open from 9:30 am until 11:45 pm... at this location, try to arrive about 30 minutes prior to closing, as the lines to buy PI tics can be long.
When you go to get you AP, just remember than anyone over the legal age to drive will be expected to bring a Drivers license/permit/ID.
If you are a Florida resident looking to get the discounted AP or any of the Florida resident tics and are of legal driving age, you will be expected to have one of the following 5 forms of ID proving your residency (no exceptions are made!):
A Valid Florida Driver's license
A Valid Florida state issued ID from DMV
A Valid Florida school or college ID w/ picture
A Valid Florida Voter Registration card and valid picture ID w/ signiture
A Valid Military ID WITH papers stating that you are stationed in Florida.
If you are a Disney Vacation Club member, you are entitled to a discount on Annual passes or Premium Annual passes only (there are no discounts on tickets or Seasonal passes). You will need your DVC membership card, as that information must also be entered into the computer as well, and a valid driver's license/state issued ID.
Hope this helps!