I'd say Qua at Ceasars. Definiately a lot of gays go there, as well as straights. I love the roman baths but nothing sexual but have chatted with a couple gay people before while relaxing in the one roman bath hottub and the tea room before.

I have used their spa services and think those are overpriced. A facial is $155 (But I do use spa finder coupons which are 20% off at costco during christmas time and you don't have to pay the $45 spa admission so I have to take that into account) and the facial only lasted 45 minutes. The massage I had last year was also pretty expensive and wasn't the best I have had. But most hotel spas overcharge.