The city bus system exists in name only. Also, you'd better be good with maps and navigation. No guts, no glory. Girls hang around outside or just inside under the telltale pink fluorescent lights. The act is usually performed very quickly, without foreplay.
Asian guys seem to have a bent toward that.
As an earlier post aptly put it, the whole experience is about as base as it gets. Condom usage and insistence is excellent, probably much to the credit of an NGO or two doing educating in that area. No problem, really. They don't really expect you to make much conversation. The Vietnamese ones will be pretty aggressive anyway.