NOGALES, Sonora — Along Boulevard El Greco, construction crews and bulldozers cross the busy street while just beyond the dust clouds, a pair of large retail centers are quickly taking shape. The new 250,000-square-foot Nogales Mall and the 130,000-square-foot Wal-Mart Supercenter are under construction at the city's southern edge. At the same site, a new Peter Piper Pizza and a Carl's Jr. are getting ready to open their doors, alongside a new Applebee's Neighborhood Grill & Bar. Touted as the largest mall to be built in Sonora, with the city's first pair of escalators, the Nogales Mall will have 114...