Pancho's has been on Playa Gaviotas in the Zona Dorada since 1985, and is what people mean when they talk about Mazatlan beach seafood. The dining room sits directly on the sand. The menu is what you would expect — aguachile, ceviche tostadas, garlic shrimp, whole grilled fish — done well and in generous portions. The margaritas are strong; the prices are firmly tourist-zone but not unreasonable.
The roving mariachis are part of the deal. Sunset is the time to go, and Tuesday-night Mexican Fiesta with folkloric dancers is a touristy tradition that has been running for decades.