Thaw fish, if frozen. Rinse fish, pat dry with paper towels. Cut fish into 3/4-inch strips. For marinade, in a shallow dish stir together margarita mix and jerk seasoning. Add fish strips, turning to coat. Cover and marinate in the refrigerator for 15 minutes, turning fish once or twice.
Meanwhile, for salsa, in a large bowl stir together the beans, mango, tomato, cilantro, green onion, jalapeno pepper, lime juice, ancho chili powder, and salt. Set aside.
Drain fish, discarding marinade. In a 10-inch skillet cook fish in hot oil over medium heat for 2 to 4 minutes or until fish flakes easily with tested with a fork, turning fish occasionally. Meanwhile, heat tortillas according to package directions. Fill tortillas with lettuce, fish strips, and mango salsa. Serve immediately. Makes 4 servings.
Make-ahead directions: The salsa can be made ahead and chilled for up to 2 hours. If chilled, it should be allowed to stand at room temperature for 30 minutes before serving for best flavor and so it doesn't chill the fish when you add it to the tacos.