I think you place too much importance on the supposed pious intentions of the people at Dos Ojos.
When you reach the entrance the guard there asks if you are a diver or a snorkeler, he then proceeds to collect your money.
It's when you get to the parking lot that the other guard asks for a "full cave" cert. What happens if you left it at the hotel, you turn back to get a refund? Fat chance.
I did not brag of having used a bogus card, I did what I had to do to get in and do my 10th dive of the week (at my intro cert level). I would have used my Mickey Mouse club card if possible. (BTW I'm racking up experience and practice to go for full cave in a year.)
I wanted to raise the point that there is the beginning of an attempt at controling the cave diving environment in the peninsula, the future will tell.
I understand that the situation is very different in Florida and I have absolutely no problem with the rules and regulations that are in place, for example at Ginnie Spring.