Place the seafood in a bowl. Add oil, lime juice, cayenne, sugar, ginger, garlic and cilantro. Gently toss and marinate 30 minutes. Thread the mango, green pepper and seafood on long skewers. (Each skewer should start and end with mango and green pepper. Each should have 2 scallops, 2 prawns, 2 pieces of salmon, 3 pieces of green pepper and 3 pieces of mango). Grill over medium-high heat 3-4 minutes per side, or until just cooked through.