Desperado is great, and Canyon Blaster is a very smooth double loopscrew (plus the theming is fun). I would not recommend Manhattan Express to anyone. I'll be going on Speed for the first time next month (has been closed every time I go to Vegas).
Word of advise, if you are going to Las Vegas, prepare to spend a lot of money!
P.S. Desperado is about an hour's drive, and was something like $8 per lap, the other rides at Buffalo Bills will most likely be closed, and there isn't much else to do in Primm...just a heads up.
I'll think of some fun Vegas things to do and post them here.