There are two ways to claim a huge exemption (about $90,000 p.a.) on your US taxes. You must either:
1. Be out of the country for at least 330 days in any 12 month period (if you meet this requirement, you have an open and shut case for the exemption).
2. Have an "established residence" in another country. This is a little bit of a gray area, and I get the sense that the IRS might fight you on this if they don't buy your story that you really live overseas but you spend 3 months a year in the USA.
I hope this helps!