Place fish in a non-aluminum dish large enough to hold it in a single layer. Combine tequila, triple sec, lime juice, salt, garlic, and 2t oil and pour over the fish, rubbing all over. Cover and marinate for 1/2 hour at room temperature or up to 3 hours in the refrigerator, turning occasionally. Just before serving, combine tomatoes, onions, chilies, cilantro, sugar and salt to taste. Heat the grill to Very hot. Remove fish from marinade, pat dry (reserving marinade) and brush lightly with 1 t oil and grind pepper over the surface. Cook on a greased grill for about 4 minutes per side, or until flesh is opaque. Meanwhile, boil marinade in a saucepan for 2 minutes, remove and discard garlic cloves, and spoon a little over the fish. Spoon the tomato salsa along side and serve.