We did back to back cruises out of Mobile, Alabama. We had to get off the ship to register for the second cruise. We left our clothes on the ship, but because of a mix-up we had to move our luggage to another room for the second cruise. It all went very smoothly and we had a great time.
From what I understand (our 1st B2B won't be until October !) they will ask all the B2B cruisers to meet in a certain area on the ship with their passports. They'll escort you off the ship, through customs and back on.
Since you've booked so far out you should be in the same cabin. If not, your Room Steward will help you move to another cabin.
Have a wonderful cruise!
"A truly happy person is one who can enjoy the scenery on a detour."
We did a b2b on the Valor in 2005. I booked the same balcony cabin for both weeks so we did not have to pack and move. When we arrived back from the 1st week, we met with others doing a b2b (in the main lobby area) and an officer walked us off the ship with our documents, through customs and then right back on. Took maybe 15 minutes. It was really great waiting in the sitting area and watching the other passengers leaving knowing that we would be sailing for another week. Also, Carnival does acknowledge you as b2b cruisers. We received special treats in our cabin the 2nd week and were invited to a special captain's cocktail party. Hopefully, this will help.
The only way to guarantee that you will have the same cabin each week is to choose your cabin when you book. If you do the Gty cabins, that leaves it open to have to move. However, you will not have to leave your bags in the hallway the night before. Your cabin steward will have them moved for you.
My first B2B was in May 2002 and at that point, we did not have to get off the ship to check back in. They had us check back in at the Purser's Desk. I am not sure if this had to do with the fact that the second week was docking at only US territories or not, or if Homeland Security eventually had them change the policy.