I am posting the info from the AAA South site below. No residency required. Doesn't look like you can buy your pass in the midwest though.
2-Park Pass (Silver Passport) Information - #1
11/1/2002 - 12/31/2002 The 2-Park Silver Annual Pass is back, and it is discounted $30 exclusively for AAA members! Pass is valid for unlimited visits to both Busch Gardens & Sea World for one year from first redemption of our certificate at either park. The pass includes free parking (except on first visit) plus discounts on food, merchandise, guest admissions and more. Florida, Georgia & Tennessee branches will carry these passes and they can be sold to any member - there are no residency restrictions.
2-Park Pass (Silver Passport) Information - #2
11/1/2002 - 12/31/2002 Tickets must be redeemed by March 15, 2003. Members can purchase tickets for family, friends or gifts and they do not need to be present when the pass is redeemed. The tickets must be exchanged for a photo ID pass inside the parks. Guests will go directly to the turnstiles with our ticket and then proceed to the Pass Processing Center to get their photo pass. There will be signs posted with direction to that area.
2-Park Pass (Silver Passport) - Adult Price
At the gate: $129.95
At your AAA Auto Club South Office: $99.95
AAA members save: $30.00