SAN SIMÓN EL ALTO, Mexico — When Alejandro Cedillo was deported to Mexico from the United States, his Florida-born son and daughter were little older than toddlers, and it would be six years before he would see them again.

Mr. Cedillo returned, alone, to his close-knit family in San Simón el Alto, the hilltop farming town he had left nine years before, when he was only 17.

To an outsider, the gold-green fields rolling across Mexico’s central plain seem to promise a chance at a decent living. But drive into places like San Simón, where the concrete houses stand incomplete and the paved road peters out, and the poverty that drives people to leave for the United States comes into focus.

Like Mr. Cedillo, now 32, many of them eventually come back. Some are deported; others return to care for a sick parent or simply decide it is time to leave the United States.