I have been to several spas in Vegas...Luxor used to be 24/7 but no longer. You can go there as an ouside guest (at least you could last year). It has a good steam room.
Flamingo has a small steam room but the hot tub area is isolated somewhat and can be a little touchy/feely. <G> There was a guy in one tub and I went to another one since it was just the two of us back there. I saw him get up and walk out of the area five minutes later and boy did he have the most beautiful soft cock I have ever seen. Seriously! I chatted with him in the lounge area in our towels and wanted to see more, but alas he was straight (based on what he was saying) and not there for that I guess. At least I have my memory!
Bally's was good from the past but did not accept anyone who was not a guest the last time I visited.