I know there are groups out there (yahoo?) devoted specifically to lapbanding in Mexico but I don't know the url's. I have heard both good and bad about Mexico but if you do your research you should be fine.
The HUGE caveat I've heard from lots of people about being banded in Mexico (or other far away locations) is after-care. You need to see a follow-up doctor roughly once a month for the first six months (YMMV) to get fills and check on your progress. Often local doctors won't take on someone who's had the surgery done elsewhere. I've heard lots of horror stories about people who thought they had aftercare lined up only to find out it fell through. Apparently some Mexican surgeons will give you a list of doctors in your area to do aftercare but when you actually call them they won't/don't take Mexican patients.
Also, the cost of a fill can vary widely so shop around when you are lining things up. I've heard of some self-pay patients getting 6 months or a year's worth of fills as part of the total package. I've heard as low as $150/fill and as much as $600
Good Luck,