I was up there last november, and talked with the guys that do that "thunderball of death" thing up on "fairmont" or where ever that big overhead screen is. They said there weren't many good motorcycle road up that way. I have seen that if you rent cars up there, there's supposedly some good senic mountain roads to the north, I think. that might be worth checking out.
Some sportbike guys told me about Red Rocks? The hills just west of the city. I don't know if that would be suitable for a tard or not...but I'm up for a trackday too, if there's anything like Grange out there!
I always wanted to ride the old XPlex...too bad the city took them over
Red Rocks looks like a nice ride but not a "fun" ride. I've not seen any twisties near Vegas. There is a tack in Pahrump (about 45 min. North) ((Note: prostitution is legal in Pahrump)) but I don't think you can show up and ride. There are some orgs that do track days there though. http://www.springmountainmotorsports.com/track-map-layout/