Gambling and glitz are just not my cup of tea, so I find Las Vegas the most tiresome city I've ever visited.
If you want something different, and have a car, take a day trip to Death Valley National Monument. It's about a two hour drive. Interesting sights, people, and it's the absolute antithesis of the cities that you will be visiting. Nothing like looking UP and seeing a sign that says "SEA LEVEL" a couple hundred feet above your head. Also a nice warm-me-up after Montreal. Temps could push the century mark even in February.
Lindy