Mix juice, oil, salt and all of the spices in small bowl. Place chicken in large resealable plastic bag or glass dish. Add marinade; turn to coat well. Refrigerate 30 minutes or longer for extra flavor.
Heat large skillet on medium-high heat. Add chicken and marinade; cook and stir 5 minutes. Add bell pepper and onion; cook and stir 2 to 3 minutes or until vegetables are tender-crisp and chicken is cooked through.
Spoon chicken mixture into warm tortillas. Serve with assorted toppings, if desired.