Activists say public isn't only culprit — leaders and companies are also culpable MEXICO CITY — Mexicans have become world-class litterbugs. Soft drink bottles, snack wrappers, used diapers and cigarette butts clog city streets, rural highways and scenic beaches. Mountains of garbage stand sentry-like in empty lots and at the edges of bucolic rural villages. Discarded plastic bags hang in trees and dangle from cactus like bitter industrial fruit. Not every Mexican litters, of course. And perhaps no one does so all the time. But enough of them do, enough of the time, that this nation of 105 million people...