So to get the best rate, you have keep looking right up until the time you leave. Here is what I do to save money. First, I go through Ebates.com. You get a gift card just for signing up. Then you use their site to go to travel sites to book your car rental. When you do, they give you money back, sometimes 3-4% back in cash. We are flying into SNA also and I started looking months ago. We need a car for 8 days as well. Originally when I started looking it was going to cost $300 or more for a standard car. About 1 month ago I went into Hotwire and to see what they came up with. They showed that I could rent a car from Alamo for about $265 or so. I logged into Ebates and then went through Ebates to get to RentalCars.com to rent a car. RentalCars.com was offering 3% back through Ebates. I booked a car, no payment needed. Then I started watching things. A week later I saw on Hotwire that Thrifty was much lower, more like $225 so I went through Ebates again and used their connection to Thrifty to reserve a car plus got 3.5% back from Ebates. I cancelled the reservation through RentalCars.com. Then the next day I went in again to Ebates and saw that Thrifty was offering 15% off a mid size SUV PLUS the 3.5% back through Ebates. So I went in and booked a midsize SUV with the cost being (with taxes) $185 for 8 days.
The key is to keep watching the rates and don't go through someone you can't get your money back from. I use hotwire to see what the rates are for the various companies but I don't book a nonrefundable rental through them unless at the last minute they are cheaper.
I hope that makes sense.