Ralph Rubio admits he was “naive” in the beginning. The year was 1983. He was about to launch a new eatery in a former Orange Julius stand near the beach in San Diego, backed by his father. The featured attraction: a fried fish taco. It was simple and, he thought, delicious — a flaky white fillet dipped in batter, nestled in a soft-corn tortilla and topped with creamy white sauce, a dollop of mild salsa and shredded cabbage. He discovered the delicacy a decade earlier, on college spring break trips to the Mexican beach town of San Felipe on the Baja California peninsula. For Rubio, the fish taco was love at first bite. He thought the masses would be similarly hooked.