Yes. While the minimum age for drinking, gambling, or being around those activities is 21, there are some hotels, including those with casinos, that permit those aged 18+ to check in, provided you have valid I.D. and, generally, a credit card in your name.
There are too many hotels in town for us to call every one, but we did a pretty comprehensive survey, based on places that historically have allowed check-in for those aged 18 and older, those properties that were rumored to, and other places we guessed might permit this. Our findings were surprising, in some instances, and on more than one occasion we were informed that state law prohibits this -- even at non-gaming hotels -- which is not the case. Here's what we found:
Hotel-casinos that permit check-in for those 18+:
Non-gaming hotels that permit 18+ check-in:
Interesting list of places that don't, which we thought might:
If anyone knows of anywhere else we missed that permits those aged 18+ to book a room, please let us know. Note that there's also a curfew on the Strip: From 10 p.m. Sunday through Thursday and midnight on Fridays & Saturdays, anyone aged under 18 must be accompanied by an adult.
One last thing: In the course of researching a previous QoD (01/07/2010) about activities for older teens, we discovered a nightclub in Henderson that's aimed at those aged 16-21. It's called Club4427 and here's the link to their MySpace page.