Some of it comes down to expectations and some on who you hang out with.
I've seen plenty of expats in China who think that all Chinese girls are desperately looking for a foreigner and a green card marriage. I only met one confirmed green card girl ever. I'm sure if I regularly hung out in some of the sleazier expat bars, I'd meet a few more, but I far prefer to go out to a restaurant and eat (and drink
) with friends than to spend every evening hunting the cheapest beer in town.
I've gotten the special "foreigner discount" (aka "let's see how dumb he is?") a few times. I've also gotten great deals (independently verified by Chinese friends) because the sales person wanted to make a good impression.
I've gotten a few hostile looks. I've also had complete strangers come up and share an umbrella with me when I got caught in a downpour.
If I had some freaked out pre-formed view that everything was bad, I'd probably view more experiences that way.
Overall, my interactions have been mostly positive. Then again, I usually expect things to be positive (but also randomly confusing).
Vietnam does sound like a fun place for a vacation. I'll probably give it a try sometime.