1. Place chicken in a resealable plastic bag set in a shallow dish. For marinade, combine Italian dressing, chili powder, and cumin. Pour over chicken; seal bag. Marinate in the refrigerator for 1 to 24 hours, turning bag occasionally. Drain chicken, reserving marinade. Brush marinade over sweet peppers and red onion.
2. For a charcoal grill, place chicken, pepper, and onion on the rack of an uncovered grill directly over medium coals. Grill until chicken is no longer pink (170 degrees F) and vegetables are crisp-tender, turning once halfway through grilling. Allow 12 to 15 minutes for chicken; 8 to 10 minutes for vegetables. (For a gas grill, preheat grill. Reduce heat to medium. Place chicken and vegetables on grill rack over heat. Cover and grill as above.)
3. Remove chicken and vegetables from grill; carefully slice into thin bite-size strips. Spoon chicken and vegetable mixture onto warmed tortillas. Top with Jicama Relish and salsa; roll up. Makes 8 fajitas.
4. *Note: To warm tortillas, wrap tortillas tightly in foil. Place on edge of grill and heat for 10 minutes, turning once.
5. Jicama Relish: In a large bowl combine one 15-ounce can black beans, rinsed and drained; 1 cup chopped, peeled jicama; 1 large tomato, chopped; 1 medium avocado, halved, seeded, peeled, and chopped; and 1/2 cup snipped fresh cilantro; set aside.