We reserved National for our trip in May. At the time, MS's quote for Alamo was higher than National. Disney Visa website has specials for Alamo. I plan to keep checking different car rental companies up until we leave, and if I find a cheaper one I will just cancel the National. But for the last several months I haven't found anyone cheaper. (Because we're over 50, we can get the AARP rate which seems to be one of the better discounts.)