I have not been to San Juan, but I would suggest having at least a dive master with you for your first dive. I suggest this for a couple of reasons. Fist off, for a first dive in a vastly different environment, it would be a good idea to have someone with experience in that type of environment, this includes any dives in other fresh water areas that you have not dived before. Secondly, you have to evaluate your own skill level and decide what you honestly can deal with. Thirdly, when a dive guide of any kind is with you, they will know the best places to see all the great creatures and structures. I would guess that your resort either has a dive operation within it, or they can refer you to one that is reputable. I am sure that someone here will also have some great suggestions. Have a great trip and tell us all about it when you return!
Tim
P.S. If you are going to be doing multiple dives over your vacation, or dive more in the future, I would highly suggest investing in a dive computer. If you use your dive tables correctly, and compare your dive times with a computer, you will see that your dive times will be extended with a computer and you will be able to enjoy your dives more.
