As I understand it Carnival provides transportation on the day of the cruise from LAX or SAN airports to Ensenada for the cruise to Hawaii.  We will be flying in on the day before the cruise, so I am assuming we will have to go back to the airport to take the bus.  I read also that the bus first goes to the San diego pier for check in.  Is this true of all the buses, even those coming from LA?  Thanks for your help.

There is no check-in at the Ensenada dock, so you will be checked in at San
Diego dock, then buses will take you and your luggage to Ensenada. There, your luggage will be taken to the ship and you can explore Ensenada if you wish. Ship doesn't leave until 9PM.