The Place for Alternative Cancer Treatment
All US citizens are required to travel abroad with a valid US passport or US Passport Card. You and your companion will need a passport to enter Mexico.
If you do not have a passport, click on this site for information on how to get a passport or passport card: http://travel.state.gov/passport/hurry/hurry_831.html
Some agencies on the Internet offer a shorter delivery time for an additional charge: Here is an example: http://www.rushmypassport.com/