I've been going to and enjoying a local Korean Spa near me for about a year, and my experiences mirror most of these.
First, I go for a good, long sweat and relaxation first and foremost. Enjoying being naked around other naked guys is a nice bonus, and if I see any action, then super-bonus. I'm 31, in good shape, usually shaved smooth, or at most, trimmed very short.
I've always worked under the impression that when I'm there, if a guy is Asian, they're there for the spa experience, if they're not, there's a good chance they're bi or gay. (Painting with broad strokes, I know. lol)
My spa is pretty small. The locker area is nice. The "wet" area has 5 open showers with a partition blocking 4 of them from the soak tubs. There are 3 soak tubs, one cold, one warm, one hot. Plus a dry sauna and a steam sauna. Guys are always looking to see who is around and who is going where.
There is also a (I think) "Jade Room" in the men's section which is a very warm marble-like room where you just lay down and sweat, but t-shirt and shorts (provided) are required for that room.
I'll always see guys at least idly touching themselves in the tubs and the saunas. It's inevitable sometimes, but some guys are looking for action. I've seen guys jerk off in the steam sauna, and I walked in on two guys giving head in theI Jade Room. In that case, I just said "I don't care. I'm not interested, but I don't care" and I let them go back to it while I laid on the other side of the room.
I've boned up occasionally here and there, depending on the crowd that's there and what's going on, but I generally and too scared to do anything... not wanting to get caught/thrown out/arrested or something.
I guess, other than flat out saying something, how would I signal, when I go into the steam room, that I personally am not looking to bust a nut, but don't mind if other guys do/I'd like to see? Too many times guys get bored and leave when I'm in there because I'm not really making a move.
Either way, mine is a nice place to go and escape for a handful of hours, and get to hang out naked with other guys, and you can't beat that!