If you're staying in Las Vegas and feel like hittin' a club but want to wear jeans. Check out Jet in the Mirage. This is one of the few clubs that lets guys get away with jeans. Call your hotel concierge and they can try to get you on the guest list. This way you won't have to pay cover or wait in line. Another tip is to talk to the cab drivers about clubs. Many times they have free tickets.
I've been to Jet twice and the line moves pretty quickly. Once you're in, they have 1 main room that plays hip hop and mainstream. They also have a reggae and house room. The drinks can add up but the atmosphere is awesome and the crowd is friendly.
Jet is great for people in their mid to late twenties.