In medium bowl, stir together juice, sugar, chipotle pepper and salt. Stir in shrimp, coating completely in marinade. Cover and refrigerate 30 minutes to 1 hour, stirring at least once during marinating. Heat oil in large non-stick skillet over medium-high heat. Cook and stir onion in hot oil 2 minutes; add pepper strips and cook and stir 1 minute longer. Drain marinade from shrimp; discard marinade. Add shrimp to skillet. Cook and stir 2 to 3 minutes longer, until shrimp are no longer pink. For each taco, spoon about 1/2 cup shrimp mixture into tortilla. Top with avocado, pico de gallo, cilantro and cheese. Serve with a squeeze of lime. Makes 4 servings (2 tacos each).