The Sahara has one at 11 PM, though it might be a bit far from where you are staying. For cash games, you can find games pretty much anywhere. Most rooms spread some form of low limit (usually 2/4 or 3/6, though the Wynn & Bellagio start out at 4/8), and most of the major hotels have 1/2 or 1/3 NL, except the Bellagio which has 2/5 as it's lowest NL game).

Check out allvegaspoker.com, mentioned by another poster. That's your best resource.

For a fun game, I'd recommend playing 1-2 at the Imperial Palace. Sure, it's not a gorgeous casino, but the players there tend to be more fun, and it's a more laid back atmosphere. Both times I've gone this year, that's where I had the most fun.