The Keys is a great destination for new divers, particularly Key Largo. Limit your diving to those dives in the park, Pennekamp park. The maximum depth will be 45 feet, and the visibility is good. The operators there I have dove with usually offer the option of diving with a DM, or diving on your own in buddy pairs or small groups. This is true for Amy Slate's, and for others as well. As far as preparing to dive with a paired up buddy, see my blog here on SB about diving with instabuddy. I won't re-write it here. As to navigation, every diver should be at least an ok navigator, and after 20 or more dives, be good at navigation. You don't need to rely only on you compass. Use natural objects, as in from mooring line to large barrel sponge 30 feet off. From barrel sponge to coral head 40 feet north, around coral head until I see the barrel sponge. Back to barrel sponge. Back to mooring line. Now, time permitting, go another direction with similar methodology. There is a funny thing about operators in the Keys. They understand some times a diver(s) can get off their mark and need to surface to locate the boat. Charitably, this is referred to as a "compass check." There is no shame in ascending slowly and doing a safety stop then surfacing to locate the boat, get a compass heading to it, and then descending to resume your dive. If you are sketchy on navigastion, equip yourself with a safety sausage so if you surface a distance from the boat you can inflate it and be seen. One last tip. Be sure you identify the boat you came on. Many sites may have two or more dive boats in the area. so do get your compass heading to the right boat. You will be fine. Have some great dives.
DivemasterDennis