Rinse fish; pat dry. Set aside. In covered small saucepan cook potatoes in enough boiling salted water to cover about 15 minutes or until tender. Drain and cool.
In small bowl combine chipotle chile pepper, sugar, and 1/4 teaspoon of the salt. Rinse fish; pat dry. Measure thickness of fish. Rub chile pepper mixture into fish.
Grill fish on greased rack of uncovered grill directly over medium heat for 4 to 6 minutes per 1/2-inch thickness or until fish flakes easily when tested with a fork, turning fish after half the grilling time.
Cool slightly. Break fish into chunks.
In medium bowl combine salsa, lime juice, and remaining salt. Add potatoes, fish, green onion, and cilantro; toss gently to coat.