June should be well before the stormy season!
We did the Nekton - Cay Sal Bank last year the first week of June and the water was flat - honestly, it was like glass all week. The boat was almost full, a few guys had rooms to themselves so every room was used, but it never ever felt crowded. It was our first liveaboard trip but not our last. We hope to do one to the Pacific next year, maybe Kona, Palau or Fiji. They really are the best bang for your buck.
If you don't want to do the Nekton again, are you considering another liveaboard? A couple we know went on the Explorer to Saba and loved it. They are pretty well traveled but had never done a liveaboard and say they are spoiled forever. Also, a guy we met shortly after our trip was desperate for a trip and his buddy couldn't go with him for the first time, so we recommended he do the Nekton (he had never done a liveaboard). He chose the Nekton Cayman trip last Sept and said it was his best trip ever, bar none. I think liveaboards really spoil you, so if you like them too you might want to try one again if you can afford it.
robint