On a warm May weekend in this Central Valley town, the irony was as thick as melting fudge. As usual, the annual Chocolate Festival was drawing hordes of fun-seekers. However, they were streaming in by the thousands just two weeks after Hershey Co. — Oakdale's biggest employer and the nation's biggest candy company — announced its plan to close its sprawling plant, eliminate all 575 jobs and open a new factory in Monterrey, Mexico. On one side of busy Yosemite Avenue, the festival drew children to games where they slathered their heads in syrup as their parents patiently stood in...