Some see the $5 taco as the Holy Grail. It is, some say, the highest expression of authentic Mexican street food. For others, it’s a sure sign of the impending apocalypse. Not me. I’ve been to Tacos Varios (Carretera Libre Tijuana-Ensenada KM 47) in Ejido Primo Tapia south of Rosarito Beach in Baja.