Carnival has a service in San Juan where for $15 per bag you can do the airline bag checkin at the pier and it will be delivered to the airline and loaded leaving you free for the day. You pick it up when you get to your final destination. Check with the Pursers Desk for info. Other cruise lines may offer this but I am not sure.
52 Carnival: Mardi Gras, Ecstasy X2, Fascination X6, Celebration, Elation X5, Glory X5, Fantasy X4, Valor, Holiday X3, Imagination, Liberty, Spirit X2, Freedom, Destiny X2, Splendor X2, Dream X2, Conquest, Legend X3, Victory, Sensation, Paradise, Inspiration, Magic X2, Triumph, Miracle, Breeze
6 Norwegian: Sky, Jewel, Dawn, Epic, Pearl, Breakaway
7 Windjammer: S/V Legacy X3, S/V Polynesia, S/V Caledonia, S/V Diamant, S/V Sagitta