DAYTON, Tenn. — Hearty applause arose from within the two-story house as white vans rolled up the gravel driveway to pick up a group of Mexican workers to return them to Mexico. "If God is willing, we will all come back next year," 27-yearold Francisco Ocañas said last week, speaking in Spanish. Mr. Ocañas was among the group of 29 men who spent six weeks harvesting fruit at a local farm under a guest worker program. For Mr. Ocañas, the 32-hour bus ride back to the Mexican town of Nuevo Leon is familiar. He first came to work in Tennessee...