Theresa,
Believe me, your trip will NOT be dissapointing. Normal is a relative term. Normal for this time of year, yes it is just about back, but then again, it all depends on rain, wind, hurricane season (which only does not affect us directly,) though during the season, the Caribbean Sea can churn up, making vis a little low.
I will tell you though it will be MUCH BETTER than almost ANY where in the States. You will not dissappointed if you think that their will be 100+ feet VIS every day if that is what you expect. Just think though, if you expect let's say 60+ feet and you DO get 100+ feet everyday, you can be OVERJOYED with your trip!
Liz