The 16-ounce cans have started to show up at shops here and there, labels depicting an Aztec princess, along with the Spanish, “La Chela Mas Chula.” In beer parlance, a nice cold one. At first glance, one might mistake these Cerveza Xteca cans for imported product, but the beer, dubbed Mexican Style Lager, is brewed right here in San Diego, intended for locals. The beer company’s Chicano founders originally wanted to label it “Mexican-American Lager,” but the TTB couldn’t quite grasp what that means in terms of beer. Mexico’s over there, it reasoned, America’s over here. The Federal agency struggled with the concept of a borderland identity.