That's the key! While you'll see a lot of Disney signage in your local AAA office, don't expect every agent in the office to actually have a lot of Disney experience. Some will, but your chance of getting a good one during a random walk-in aren't high.
If somebody is going to use AAA, be sure you get the assigned agent to talk about WDW in general. Gage their abilities by what they tell you, especially any "secrets". Ask some specific questions about things like Magic Bands, Extra Magic Hours, Fast Pass + and Memory Maker. You're looking for the agent's knowledge when you ask this, not really for the info. If they hem and haw about the questions, or say they will look it up and get back to you, then its time to walk away.