Your plane ticket and a passport.
To buy the plane ticket to Mexico, no... there is no ID required. But to USE that ticket and GO to Mexico then yes, you will need a passport and that will be your ID.
No. If you enter Mexico by plane you need a valid passport. If you enter Mexico by land however, it will not be much of an issue; however on your way back to the US you will have to show at least an ID or birth certificate.
Yes, you do.
There are a couple of answers for you but no matter what you need an ID for all answers I'm about to give. If you travel by bus, or any automotive you need a U.S. Naturalization Citizenship document and if you travel by plane or boat you need a passport POSTER: In response to your question. So, if you are a U.S. citizen, once you are actually in the country of Mexico, you still need to provide ID to go from one part of Mexico to another? What if you are a Mexican citizen who ONLY wants to travel within the borders of Mexico. Would he need an ID?
does a citizen of Mexico need a passport to go from the us to Mexico and back? He is legal to be in us but not a us citizen.
No. Arms and ammo are illegal in Mexico.
Plane
Yes, children need a passport to travel to Mexico.
Yes. Not a passport per se, but you need an ID to get into the plane.
get plane tickets and fly to mexico
True: Australia is on the Southern Hemisphere, while Mexico is on the Northern Hemisphere.
Indeed.