By the way, I called the "800" number and was told the code was fine. To double check I called the Alamo counter at the Orlando airport and was told that if the computer let me book it then it was fine.
I didn't have to have a car so signed up for the magical express just in case. We ended up taking that and saving $215!
But the counter agent taking your call didn't ask questions to find out if you were qualified to use the code whereas the counter agent serving you when you get there might.
Did the booking computer ask you enough questions to determine if you were qualified to use the code?
In general you can't trust anything anyone tells you. Customer service agent or via e-mail. What matters is what the counter agent and manager will do. Even calling them directly means nothing. We called the Alamo counter at MCO to ask about the new standard car class. They knew nothing.