I used to get excited about bootleg DVD's from China, but eventually realized they're a complete waste of money.
The packaging is often inaccurate. The quality is typically roughly equivalent to VHS at best (and all too often is camcorder-in-the-theater). US movies are usually region 1 or no-region, but movies from other parts of the world (especially Europe) are often encoded for other regions or sometimes even PAL (most Chinese DVD players are multiregion and tv's are dual-system PAL/NTSC).
And I can't tell you how many bootleg DVDs I've seen that stopped working 10 minutes before the movie ended.
When I lived in China, it wasn't such a problem, because many of the local bootleggers would accept returns of defective discs (seriously). But when you're buying in bulk to return to the U.S., odds are you're going to get a lot of crappy ones, which increases the price-per-workable-disc quite a bit.
For my money, I'd rather pay $2 and rent DVD's at my local video store. If they don't work I can get my money back, and the picture and sound are actually DVD quality. Plus I'm supporting local small business instead of international pirates.
But if you insist on bringing some bootlegs back, you probably won't have a problem as long as you aren't bringing multiples of the same title. I wouldn't ship them, though, and keep in mind that they're really not legal.