The fee for an additional driver (including spouse) is around $10/day. The fee is waived with many corporate codes and some of the promotional codes we use such as COSTCO. The fee is also waived for members of quicksil*er.
THANK YOU for your quick response! I made the ressie using car rental savers http://www.carrentalsavers.com/florida-car-rental.html (which is travelocity, i think). While I was posting my question here, their confirmation email showed up in my inbox, and when I used the confirmation number to look at my ressie on Alamo's site, it specifies contract ID 430710 and 1 additional driver included.
I have usually found great rates with that website, and I now have a full-size car for less than the midsize I booked 4 months ago. Wahoo!!!