I use autoslash.com too which has always listed priceline as the cheapest option of those they offer. Through autoslash/priceline I have gotten Alamo, Enterprise, and National. I've looked into other car rental sites but autoslash has almost always had the best price. I think kayak beat them once for me. I am an Alamo member and it seems that times I have checked with them directly versus autoslash/priceline, an Alamo car was cheaper with the latter or the same. I do not have a Costco or AARP membership. I also stay away from those cheaper places, because it sounds like too much can go wrong. I have had bad costumer service with Alamo - mostly very rude employees that act like they would rather be at the dentist. I was treated like a moron because I declined their insurance. Tip: always bring proof of your own car insurance. Some companies make you get theirs if you don't. Also at Alamo I had to wait 45 minutes to talk to an employee and get the car I reserved event though there was only 1 other person waiting when we got there (that was in Anaheim), but that is about it. Another tip: bring change to use at the tolls if you don't want to use the sunpass system.