Hello! I'm assuming that you have a Sailor on the USS George Washington. All FPO addresses are different, according to what area of the ship your Sailor works in. You can contact your Sailor's recruiter or contact the ship's Ombudsman. A good source of information is
http://gw.ffc.navy.mil/
Also...join Navy for Moms. It's a great website for families to communicate and there is a group especially for the USS George Washington. When you join, hit on the "Groups" Tab, type in "USS George Washington" and click on the site with the most members.
All the best to you and your family! Welcome to the Navy!
My name is Chris and my email address is phip48@yahoo.com I have a son serving on the flight deck of the GW.