We stayed there when it was Rock's Inn (I believe it is the same place), and it was a nice hotel with one exception. It was very windy when we were there, and all of the rooms had gas stoves in them. We had our windows open to get airflow, and most of the people in our group did the same...well it blew out the pilot lights on the stoves, and slowly filled all our rooms with gas fumes. We all couldnt figure out why we all had headaches and were feeling sick to our stomachs whenever we stayed in the room very long. Once we figured it out, we shut off the gas to the stove and were fine. I believe they have upgraded some since then, but it might be something to think about if it is windy.
As for Blue Hole, we chose the Turneffe trip instead. I was told that the Blue Hole makes a nice oddity to check off on your list, but for visual stimulation, its kinda humdrum. Turneffe was by far the best diving we did while in Belize, and if I ever go back, it will be to stay at Turneffe Lodge or Manta Resort on Glover's Atoll. The trip to Turneffe and the trip to Blue Hole are roughly the same distance and are both all day trips, so if you have the choice, I would do Turneffe.
Good Luck and let me know if you need more information.
AggieDiver