From what I understand, Mark, there’s not a lot of exciting dives in Puerto Vallarta, but there is some diving industry there. Probably 3, 4 operators to choose from? You should find diving if you look for it but don’t expect it to be on every resort menu. ;)
I know that’s not the most helpful, but seeing that nobody’s offering any further tips - I thought I’d give you my take. (I looked into it a few years ago as a possible dive destination and decided to pass)