1. Place chicken in plastic bag set in a shallow dish. For marinade, combine dressing, chili powder, and cumin. Pour over chicken; seal bag. Marinate in the refrigerator 1 to 24 hours, turning bag occasionally. Drain chicken, reserve marinade. Brush marinade over sweet peppers and onion. In a large bowl toss together jicama, black beans, tomato, avocado, and cilantro; set aside.
2. For a charcoal grill, place chicken, peppers, and onion on rack of an uncovered grill directly over medium coals. Grill until chicken is no longer pink (170 degree F) and vegetables are crisp-tender, turning once halfway through grilling (allow 12 to 15 minutes for chicken and 8 to 10 minutes for vegetables).
3. Remove chicken and vegetables from grill; carefully slice into thin bite-size strips. Spoon chicken and vegetable mixture onto tortillas. Top with bean mixture and salsa. Top with shredded cheese and sour cream, if desired. Roll up. Makes 8 servings.