TIJUANA, Mexico – I parked on the U.S. side of the San Ysidro Port of Entry, and after clearing passport control and walking down a barbed-wire-lined corridor, a turnstile to Tijuana clink-clink-clinked as people passed from one country to another. I got into the first cab I saw, its windows cracked open in the heat, and a driver took me through the city’s dusty streets straight to Caesar’s, the spiritual home of the Caesar salad – the original, born on Mexican soil in the restaurant of an Italian immigrant, and, as legend has it, on the Fourth of July.