Why are there so many Mexicans working in the informal economy?

Because the Mexican unemployment rate is very high and because wages there are very low. The slums of Tijuana and Mexico City make American slums look pretty good - even people on welfare have running hot water, tubs, indoor toilets, and ranges and ovens. They might prefer to go to Spain, but it's cheaper and easier to go to the USA. That's why.

They just come and go. They need sound policy at home.WE need to help them.

Why are there so many Mexicans period? It's as if all they do is have sex, do yard work, and shoot illegal fireworks.

Farms are offering $15/hour to pick produce and all those Americans without jobs are not stepping up. Strange about that. Farms are going bust because undocumented people are going back and not coming here any more. The few that remain know they are being hunted by the gestapo.