And I'll jump in her and confirm that it is Deck 3, the Lobby deck you enter into in Galveston. This is into the main atrium where the shore excursion desk and the Purser's desk is. Dave suggestion of going aft to find a elevator is a good one, but you'll have to go down a deck to the main deck because one deck 3, you will be blocked by the galley from going aft.
You can still use the glass elevators and I think they only shut down HALF of the forward (main) elevator bank for luggage delivery. But if there is a huge crowd, I suggest going aft or taking the stairs.
Have a great cruise!
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013