[Wryknow]

It really depends on the out fit. A top-quality dive shop (Al Dora is really good) was like $80 for a 2 tank dive last time I was there. You're going to need to present your certification card there though before you book the trip. (You are planning on getting certified first, right? ) They will provide you with nice equipment, a good dive instructor, and a small, well supervised dive group.

Personally I tend to go with the "budget" places myself. I've been diving for a while though so the extra hand holding is not something that I want in a dive outfit. Last time I went I was really happy with the dive shop and the Reef Club (I think it was Sand Dollar or something like that.) I got a 10 dive card (with equipment rental) for $550 and split it up with friends. The groups were a bit bigger and we didn't get dive computers but the reef looks the same no matter who you dive with.

One word of advice though. Mexican law is VERY different from US law when it comes to litigation. In the US, if you do something stupid the company gets sued because they let you do something stupid. In Mexico, if you do something stupid it's your own fault. This tends to result in very different attitudes with the dive masters. The "discount" Mexican dive outfits I have dove with are all good and absolutely want you to be safe. They keep an eye on you and the dive boat is always right there but if surface. Just keep in mind though that if you wander off somewhere they're not going to hang around and wait for you. They're going to assume that you'll catch up. If you run out of air then you need to get yourself to the surface and wave for the boat to come over. The dive master may never ask you how much air you have during the dive. If you need to add more weight because you ate too much at the buffet and can't sink now they're not going to hold up the dive for you while you try to add another 5 lbs. (In other words, they sort of presume that you know what your doing already.)