I just spoke to a Carnival agent and was told that a few hotels (they will give you the list of names) do offer hotel check in for the cruise, BUT it is never guarenteed. It depends on the number of cruisers booked at the hotel and the decision is made that morning as to wether or not they will send an agent over to begin early check in. They will not give you a number of how many people are checked in and booked on the cruise to help in your decision making! The hotels rates that were given to us were double any other hotel we were reccomended to stay in, so depending on how much you want to spend and how much of a gambler you are will factor into your decision.
Have a great cruise!