Extreme caution should always be used. You might avoid Aids but you can get other nasty stuff like the clap. I knew one French man who contracted syphilis in China. SOme cities in China now have a 72 hours visa that are given without medical checks, or even just a plain tourist visa that people use to go partake of the locals.
I hear you about those bar flies. Sometimes you just have to say no and go home alone. This goes with what I tell new teachers: "Say no more than you say yes."

There will even be god knows what disease ridden men flying into BJ or SH for whore-banging weekends/stopovers en-route to other places. HK guys have been doing it regularly in Shenzhen and Dongguan for years already.

For Russians and Koreans especially, they are going to have loads of cheaper whores right on their doorstep. I even think that some of the Japs in Dalian, do enjoy making use of those 15 day visa-free stays, lol.