Anthony Gutierrez looks for receivers during a drill as Club Aztecas de San Luis prepares for a flag football tournament. (Photo by Josh Martinez/Cronkite News) SAN LUIS RIO COLORADO, Sonora, Mexico – A group of teenagers kneel in a semicircle around five men on a small soccer field in this border city 25 miles south of Yuma.The sun has set but the sweltering heat of the Sonoran Desert remains. The dirt lots of a secondary school surround a turf field. Four light poles bracket the field, but only three of the eight lights are on . . .