U.S. tourists may visit Puerto Rico and the U.S. Virgin Islands (St. Thomas, St. Bart and St. John), which are part of the United States, with an official photo ID, such as a valid driver's license.
In addition to requiring a current passport for entry, some countries in the Caribbean may require a visa or that a tourist's passport be valid for a specific period of time after visiting a particular country. Check with the U.S. Department of State or the country's official website for specifics.
Entry by Cruise Ship
Cruise ships that visit Puerto Rico or the U.S. Virgin Islands probably also have other countries on their Caribbean itineraries, so most lines are now requiring that cruisers carry valid passports.
Since 2008, U.S. Passport Cards, or PASS Cards, have been available to people who regularly cross land borders and/or sea ports between the U.S. and Mexico, the Caribbean, Bermuda and Canada. It is smaller and costs only $45 for adults. Note that it is not valid for international air travel.
Your passport is your most prized possession when traveling, so be sure to keep it locked in a safe place at all times. Make a copy of the photo ID page and keep it in a separate place. If your passport is lost or stolen, having this copy will help expedite your passage.