There are a lot more mexicans in the states than the other way around.<br />
You would stick out pretty good in Mexico.<br />
Not to mention kidnapping americans is a lucrative trade,<br />
in less populated areas.
I was going to say the same thing mexico must look like a ghost town by now
I think you would stand out.
Check out this link.<br />
http://travel.state.gov/travel/cis_pa_tw/cis/cis_970.html#entry_requirements. <br />
This will tell you everything you need to know.
How would you know- they are well hidden