I agree with Elbert.
My son and I went to CC for our PADI Open Water certification in February '08. If I had it to do over, I would do the classroom stuff at home and then the diving at CC. You'll lose two days (arrival day + classroom day) if you take the entire course on CC.
We used Belize Diving Service and they were FANTASTIC. Pablo was our instructor and he was wonderful. I highly reccomend them.
Either way, best of luck!