The only time I've ever been asked for AAA ID was at an HI Express Munich Airport, and of course didn't have it (why carry it to Europe) - the rate differential was quite a bit more than the usual 10%. After much to and fro, the agent agreed that if I could log into my AAA account on a PC in the lobby and show her my profile, she'd accept it. Fortunately, despite my fatigue (having flown SFO/LAX/MUC), I remembered my password.
Now, I have scanned PDFs of all membership cards on my tablet.