I also live in the DC area and there are shops in your area that will put you in the swimming pool for three to four days of repeated drilling. By the time you are done with such an extensive pool work you are already a diver and you are only learning ascent control and navigation in the quarry. The quarry with limited vis is the most suited place for it because I learnt my underwater navigation in 100 feet vis and it was a freaking joke! Once you have done your checkout dives in quarry conditions, Caribbean diving is a piece of cake.
While Caribbean makes great diving destination it is far far from being the best training destination. I am not sure how many days of pool work you did prior to being introduced to the ocean but if you told me that your dive operator did not even have a pool and you started with your skills in the ocean itself then I would not be surprised.
Like Captain Sinbad mentioned, you might try Lake Phoenix down by Richmond in the warmer months. Typically in the mid to high 70's above the thermocline from June to October, and the visibility is usually pretty good. I like teaching there. A standard 5mm should be just fine. Even a 3mm works July and August.