Hi Sharon,
There doesn't appear to be a rent a wreck in vegas (no web presence - and a call to a number I found rang 10 times before I hung up).
I usually use Alamo or Budget for 2 reasons:
1) less lines/humans - faster to vegas fun with less hassle.
2) usually cheapest after using their coupon codes
if you're not signed up with these 2 online, you should do that first. I think Alamo is one sign up, and Budget is a sign up for club then join fastbreak (can't remember).
Alamo seems the slightly better company with slightly better fleet and slightly quicker 'out the door' ease, but sometimes Budget is cheaper.
Alamo codes that are good seem to be Costco code 7014627 and coupon code AD2359FDF. usually though you have to wait closer to your date to use more current coupon codes provided by alamo insiders.
for Budget, X443000 (entertainment member discount), although sometimes costco discount is cheaper W852863.
these codes will vary over time, and your mileage (ptp) will vary with these codes as well.
I'd look @ these 2 companies and rent the cheapest now. (Don't pay anything up front. Budget will charge you $10 to change a reservation that you've already paid for.) then do the same date check every now and then on both sites - if it's cheaper, book it and cancel the original.
when you get to the airport/rental facility, have your rental confirmation number, and your rental company membership cards (they'll mail them to you) with you. alamo has kiosks where you enter your info. Budget has a shack in the parking deck where you show the person your fastbreak card and reservation.
having said all this, Dollar is worth a look as well. sometimes their rates are just cheaper than the other 2. vegas4locals.com has a 10% discount if you click through.
hope this helps,
Perro