Greg,
Last time I was there, I hired through Hertz, booked the car via inter web whilst here in Oz, got over there car was waiting for me, they had one way hire, which was fantastic, showed I.d, paid some money and off we went.
We had the car for a week drove from L.A to Vegas, down to Grand Canyon and then dropped the car back to Vegas and flew home from there.
Hertz were Very easy to deal with and well organised, also managed a free upgrade, so ended up with a Lincoln Navigator.
Would recommend them hands down,
Cheers
Keith