I picked up my Mom on a Sunday from a Holland America cruise and supposedly I was to pick her up at 9am. For some immigration reason, she didn't get off the ship until 10:30 and she is a citizen with her passport and all but someone else had an immigration issue so the whole ship got behind. Not sure why but it can happen. Then again, I've been on cruises where I have my carry on and they let me off just after docking as long as you don't have luggage that they have to porter for you.
I think your pushing your luck with this. If your feeling lucky then more power to ya but I wouldn't trust it. Murphy is alive and well in South Florida.