To fly into Mexico you HAVE to have a passport. As of right now the only way you can get into Mexico without a passport is by land travel, but that will change as of Summer 2009. As of Summer 2009 you will need a passport for any land travel into Mexico and Canada.
Only if you travel by land and stay within 30 miles of the border.
Yes
No, for international travels, you really need your passport. However, if you plan to land or sea travel to Mexico or Canada and you have your License and your Green Card and Birth Certificate, then you can but you still need the passport when you get back to the US for easier travel.
Yes, provided you have a passport (flying into Mexico) or an ID/birth certificate (entering by land into Mexico).
A passport if flying there or a driver's license if going by land.
No. A passport is sufficient to travel to Mexico. A birth certificate is not valid for international travel. If you are traveling by land or sea, then you can enter Mexico with a US passport card, "enhanced" drivers license or "enhanced" non-driver ID.
A passport (air travel) or ID/birth certificate (land travel) and some money to spend are all you need.
Anywhere, if entering Mexico by land. This is an ongoing issue which has not been addressed properly: an increasing flow of illegal Americans living and working in Mexico. See related links for some insights.
Yes, you can travel by land or sea from the United States to Canada, Mexico or the Caribbean and back again using a U.S. Passport card. To travel by air or outside of North America, you will need a traditional Passport booklet.
If you are not a citizen of Canada then you can't. You either have to have a passport, passport card or enhanced Driver's license.
The passport card was created to facilitate the frequent travel of Americans living in border communities. It can only be used for land and sea travel between the U.S. and Mexico, Canada, the Caribbean, and Bermuda.