Mexico isn't third world. The only true third world country in the Western Hemisphere is Haiti.
I've been to Tanzania. GDP = $150 per PERSON PER YEAR! Now THAT is poor!
Should you go one day take extra money to grease the check points, they will take it all if you present it all... so carry small bills and hide some in your skivvvies, socks, tape some under you arm pit(shave) and maybe hide some in the lining of your clothing.
What is amazing is lately I've been ripping on Mexicans and Salvadorians - I tell them that their countries have nothing to offer them. They give me a hapless stare as if they know I'm speaking truth to them and then they reply "It's only a corrupt few in politics that has our countries like that".
Disgraceful....