I don't know that the fair would be diffrent after 5:30pm...but you may want to double check the time on when you need to be back to the ship...we set sail from Nassau around 5ish. And I have heard of many others leaving then also. Almost sounded like they were changing the time. But then again..it could just be a rumor.
Another thing...If your just going to the casino..and not on any of the DCL excursions to Atlantis...you may want to just check on getting there on your own in the first place. It almost sounded (from your post) like you were going as a group/tour...and may need to find another ride back if your group/tour left before you.
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