The rules have changed for Passports. Now if the cruise is a "closed loop" (begins in a US port and ends in the same port) you DO NOT need a passport. You can use an original birth certificate. Having said that it is always good to travel with a passport because if you miss the ship getting back into the US will be more "fun" than you planned on! Have fun and happy sailings!
Your travel agents in San Antonio.

Glad we've had ours

Beginning Monday June 8th 2009, all US citizens traveling to Canada, Mexico, Bermuda and the Caribbean will be required to carry a passport. Without a passport US citizens will not be allowed to board a cruise ship to any of these destinations. This is the final phase of the US Dept. of Homeland Security Western Hemisphere Travel Initiative. Based on reports from our travelers the wait time for a new passport is running three to four weeks. Renewals are running two to three weeks. Expedited service is available if you are getting close to your travel date. You have plenty of time to get your US passport before any of the upcoming lifestyle cruises, that are scheduled, if you act soon.