If you are only going to have a couple of dives, the prices are pretty constant. If you book a block of dives or the more dives you make, the better the price per dive, is how it generally works. I too recommend Amigos, but there are others that are good also. Most all of the operations will pick you up at your dock, no matter which place you stay. When you first arrive, go around to a few of the shops that you think you are interested in. Check out their facilites, get a look at their gear and boats, etc., have a chat. Then decide.
By the way, I thought the JJW was always around Jan 7-9?