I assume you are bringing a boat? Hawks Cay is a good place to start, I agree with Jeff. Riding in the Keys is like most places, there are just more locations that will have glass due to wind direction and the various mangrove canals. Buy a map with depths indicated, check wind direction in the morning and go out and have a blast - riding in the Keys is very cool.
Oh, and stop at the Key Largo Coffee House on your way down. Its at MM 100.5 in Key Largo -across from Wafflehouse. Thats my family's place, great food.