I just used the Priceline code to book a 10 day rental at KOA for $245 all-in! This was on the Avis site. This is for an intermediate car class; anything bigger jacked the rate up by a huge amount.
Using the same code on Priceline gives a rate of around $450

I'm thinking it will be wise to make a backup reservation w/Hertz (best rate I'm currently getting there is $377).