Process first 7 ingredients, 1 chopped mango, and, if desired, chile pepper in food processor until smooth, stopping to scrape down sides. Pour half of mixture into a shallow dish or zip-top plastic freezer bag; add chicken. Cover or seal, and chill at least 1 hour. Cover, chill, and reserve other half of cilantro mixture.
Remove chicken from marinade, discarding marinade. Sprinkle chicken evenly with 1/4 tsp. salt.
Grill chicken, covered with grill lid, over medium-high heat (350° to 400°) 4 minutes on each side or until done.
Shred chicken into bite-size pieces. Stir together chicken, remaining chopped mango, and reserved cilantro mixture.
Place lettuce leaves on each tortilla, and top each evenly with chicken mixture. Roll up tortillas, and secure with wooden picks, if desired.