Cellular

If you're going to be in Hong Kong you might as well get a phone there; it'll probably be more convenient than getting one here and trying to get it to work there. It's likely they already have phones that are better than anything they got here, so I wouldn't worry about it. If you worry about your folks here in the states / your home country calling you, just to put things in perspective, I call my friends in Japan on their cell phones quite a bit and they don't seem to be inconvenienced by it either way.

Personally, if I were you, I'd get the phone & service in Hong Kong, and try to see if there was a way of making that phone useful in the USA. Just seems more practical that way.

Jam it back in, in the dark.