I would add that I would not expect an operator to take you to the carverns on your first trip with the operator. I would expect that they will want to see you dive a few times before getting you in an overhead that ends up at 100ft. The carvern that i dove off of El Pescador was narrow dark and deep. That said, it was my favorite dives of all time. But, if someone freeked out or had bad bouyancy control if could be a really bad situation. The other thing is that it seems that they decide where to dive on the way out to the spot based on the people in the boat. As a single diver, you will probably be grouped with other people who may or may not be at your skill level. The DM will pick a spot that works for everyone. My other advice is watch deco on your second dive each day. It is extremely easy to get a small obligation there due to the depth of the dives and usually short surface interval. Nitrox would be an easy solution, but it seems dificult to get and arrange in SP.