FYI...from the U.S. State Dept:
The new wallet-size U.S. Passport Card is a travel document that can be used to enter the United States from Canada, Mexico, the Caribbean, and Bermuda at land border crossings or sea ports-of-entry. Note that it cannot be used for international air travel. The passport card is more convenient and less expensive than a passport book.
LAND AND SEA TRAVEL
ALL PERSONS traveling by land and sea outside of the United States are required to present a passport book/card, or other valid travel documents to enter or re-enter the United States.
Land/Sea Travel
Beginning June 1, 2009
U.S. citizens entering the United States at sea or land ports of entry are required to have documents that comply with the Western Hemisphere Travel Initiative (WHTI), most commonly a U.S. passport, a passport card, a trusted traveler card such as NEXUS, SENTRI or FAST, or an enhanced driver's license
AND THIS FROM DREAMS UNLIMITED:
Disney Cruise Line does recommend that all guests, including U.S. citizens, have passports. For information in obtaining a passport, here's a link to the official government website . Due to the current volume of requests, please allow ample time for your passport application to be processed. Expedited service is available for an additional fee.
All non-U.S.citizens , including alien residents of the United States, must have valid passports and necessary visas at time of embarkation to ensure his/her ability to re-enter the U.S. upon the ships return. Travel documents required throughout the vacation are the responsibility of the Guest.These guidelines are based on U.S. government regulations, which are subject to change at any time. It is the Guests responsibility to check with their
travel agent, government agencies, embassies or consulates prior to their vacation to ensure that they have proper documentation.
Unfortunately, any Guest traveling without proper documentation, as mentioned above, will not be allowed to board the vessel.
For all non-U.S. citizens including Canadian citizens, travel documents will be taken upon check-in by a
Disney Cruise Line® representative, and a passport/Alien Resident Card receipt will be issued for presentation to immigration inspectors upon return to Port Canaveral.