Over breakfast in Tijuana in 2010, the two sides of me came face to face. I was there, a Mexican-American poet visiting from Brooklyn, with the novelist Cristina Rivera Garza, who teaches at the University of California, San Diego. It was my first trip to the area, so we were sightseeing across the border. Cristina, a double agent of sorts, keeps two cell phones, two wallets, and homes in both cities. We were overnighting at her house on the Tijuana coast.