When you leave the United States, it takes only about 5 minutes to fill out a destination registration with the U.S. Department of State. If there should be an emergency evacuation or someone should desperately need to reach you, the Department of State would know how to do it. However, they can't help if they don't know where you are. You can register on line in about 5 minutes: …state.gov/travel/cis_pa_tw/cis/cis_970.html
Just an FYI to those who might want to do it. I always register here and I also leave itinerary at home with family but when I am gone, this will notify me faster if needed than any of my family members trying to get ahold of me.