You can come and go as many times as you want while the ship is in port. The length of the tours are posted with the tour information. You can view them on Carnival's website. There are cabs everywhere should you want or need one. If you want to leave the ship and aren't in a hurry, it will be less crowded to leave about an hour or so after the ship docks. Everyone who is on a scheduled tour and those wanting to spend every minute in the port will all be trying to be the first ones off. If we don't have an early tour booked, we use that time to go eat breakfast and then proceed to the gangway when the crowd had died down some.