In a large nonreactive bowl, combine the scallops, salmon, shrimp, tomatoes, mango, onion, jalapeno and lime juice. Marinate, refrigerated, for 3 hours.
Remove from marinade and grill fish and shellfish, just long enough to get grill marks 3060 seconds. Cut all fish in a 1/2-inch dice. Just before serving drain off as much lime juice as possible from the fruit, add the cilantro, sugar, shellfish and salmon. Gently mix being careful not to break up the fruit and fish.