We"re rent the full size because DH has trouble with his hip, and getting in and out is just easier for him with a larger vehicle. Last year I rented a standard and I still haven't heard the end of it! This year we're taking a side trip to Tucson for a few days, and his cousin and cousin's wife are going with, so all the more reason to go a little bigger.
JHawk - I don't know the source of the code provided, but I tried it out for our reservation and I got the same price as when I used our insider's ID, so I wouldn't think you would have any problem. If you're concerned, why not just sign up and get your own insider #? That way you'd be sure you'd be ok.
BTW - I've rebooked twice today. Down $22 the first time, and then another $15 the second time. I love that Alamo makes it so easy - no need to give your cc info each time. I just make the new reservation and then when I have the confirmation # I go back and cancel the old one. Happy bargain hunting