I used Hotwire, watched the rates and then decided to get a premium for $18 a day, about 2 weeks 2 days out. When I got there we got a Nissan Murano on the premium isle. THe mid size were dirt cheap too. Our rental was through Alamo when the deal came through. Counter to leaving was about 20 minutes.
I guess I could have done without a car, but we did make a pharmacy run, pick up soda, and then had dinner with friends off site one night.
Ours came to a week for $18 a day, $7o in cost for under $200. The mid size was about $130 and we could have made due with that.