US Rep. Alexandria Ocasio-Cortez turned tail on Manhattan’s Fifth Avenue to avoid a potential Republican challenger as they both marched in the National Puerto Rican Day Parade on Sunday, her political opponent said. Talk-radio producer Rich Valdes told The Post that he tried to challenge the freshman Democratic congresswoman to a debate on the merits of capitalism versus socialism when he spotted her near West 47th Street. But Ocasio-Cortez “cut her handshaking short, jerked her hand back and jetted to the other side of the street,” Valdes said. “She literally ran!” he said. “I thought this was a good time...