I got my AOW from Lost Reef Adventures in Key West.
Bed and Breakfasts in Key West are a must, if you have not stayed at one before.
I recommend Harbor Inn. Close to everything and right at the Historic Seaport. Lots of choices on the rooms. They have a pool and a jacquzi. The Inn Keepers are wonderful.
Staying in Key West when you visit Key West allows you to get your drink on and walk back to your hotel/B&B, as opposed to staying sober and making the drive back North on US1. Too risky to drive drunk, as you might drive into the ocean off a bridge, into an oncoming vehicle, or you may kill Bambi (Key Deer).
Try asking for the "Heavy Metal Tour" in Key Largo and the keys just south (adjacent) to key largo. The heavy Metal Tour is a set of dives on the main artificial reeefs of the Duane, Bibb, and Spiegel Grove Ships.
They are deep dives (greater than 90 ft), so get the AOW cert and deep dive under your belt, first.
I recommend staying up North in Key Largo for your dives, then drive down to Key West at the end of your trip.