Hey Doc, try dreamcarrentals.com across from the stratospehere.
They have fair pricing and a good selection of cars there.
My advice would be to go with the lowest mile GTS regardless of your personal preference for color.
I rented a 96 GTS a few months back and was disappointed in the handling and fit/finish on the car, which I at first attributed to build quality, and was beaten with ratten whips by this board until I spoke "it's a rental" in my sleep, it had 22K on it at the time.
I do recommend going to red rock canyon for wide open cruising, be aware that with the altitude the stock GTS is running approx.350 horse gross instead of 450 though, much quicker at sea level!
give a writeup when you get back, love to hear about it, your views, thoughts on the car, first impressions, etc!
Ryan