Combine 3 tablespoons milk and 3 tablespoons juice in a shallow dish; add fish, turning to coat. Cover and marinate at room temperature for 15 minutes.
Combine remaining 1 tablespoon milk, remaining 3 tablespoons juice, mango, and next 6 ingredients (through chile) in a bowl. Add 1/4 teaspoon salt; toss well.
Remove fish from dish; discard marinade. Sprinkle fish with remaining 1/2 teaspoon salt and pepper. Heat a grill pan over medium-high heat. Coat pan with cooking spray. Cook fish 4 minutes on each side or until desired degree of doneness. Serve with mango salsa. Garnish with lime slices and cilantro sprigs, if desired.