Traveling to Mexico's "Free Zone"?

I am currently visiting San Diego and planning on going to Tijuana and Rosarito in the "free zone" for a day or two. Do I need to get an FMT when I get there? And, more importantly, what is necessary to return to the US? I have my SS card, birth certificate, and driver's license, but no passport. Are the passport regulations in effect if I'm just in the free zone? And, if I need it and don't have it, what happens -- am I stuck in Mexico permenently ("man without a country" style)?

TIA!

While I'm not sure what the free zone is (I live in Baja) you won't need a passport til 1/08. You don't need a tourist permit unless you plan to stay longer than 72 hours. Get that passport, everyone needs one.

Freedom is not free