I think a near-consensus here is that diving ability matters more than certification. There is supposed to be (and might actually be) a connection between these. Many will say that connection is often tenuous.
Heck no it is Mexico. They will decide if you are a dufus based on diving, not cards.
That being said, AOW is a fun course if not really advanced.
As is so often true, you can just read cvchief's post to save yourself reading hundreds more words in mine.
I'm a class guy. I just like taking them, and when I was in college I could take Scuba for the large PE requirement, so kept taking courses and ended up as an Assistant Instructor. I promise you my skills when I was instructing in Lake Travis back in the early 80's 3 years after I was certified were nowhere near what my son's skills were when he was a teenager after a hundred Cozumel dives and a general disdain for classes. I think there's a stronger correlation between experience (as measured by number and variety of dives) and diving ability than with the number or names of classes one has taken.
Different agencies have different requirements and degrees of rigor. Your OW from one agency might be a lot more impressive to me than your Master Diver from another. Within one certifying agency there can be a big range of instructor ability. Some agencies pay more attention to this than others
Being current also matters a lot. I've been with divers with impressive logbooks who've been out of the water for a long time and do less well than relative beginners who've been diving fairly frequently.
Personal opinion: AOW is not needed in order to dive safely and enjoyably in Cozumel. The skills that are typically part of what's taught by most agencies for courses they call that (or the equivalent) are quite pertinent to the conditions typically encountered diving in Cozumel.
you enter the tunnel at about 90 feet and come out around 125
Well, YOU do. We go the other direction.
