Another thing to factor in, right now you can cruise to the Carribean and The Bahamas with a photo ID and a certified birth certificate. I've heard that as of June of this year, a passport will be required. You can obtain a passport through the post office. Here's a link to information and fees. It's best to plan ahead and apply well before you travel. It can take a while to get one the regular way, which is the least expensive.
http://www.usps.com/passport/
I can check with our travel agent and see if what I heard about June is correct and let you know.
Once you get a passport, it is good for 10 years. Mine happens to expire April 26, 2011, so I will be doing a renewal of mine around the time of our trip, too.
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Marilyn 
If anyone would like a free Bible Study CD or book entitled "Searching for Truth", PM me with your mailing address and I'll send you one. "And you shall know the truth and the truth shall set you free." John 8:32