I made my ressies with CRO & then called later for the AAA discount. They did not ask for my card number, but I was ready to give it to them. I know I will need my card at check in. I would not wait until you get there to actually ask for the discount though. Call and ask for the discount before you go. I got a 10% discount (not 20%), so I think it depends on where & when you stay.