1Heat coals or gas grill for direct heat. Mix all Salsa Dressing ingredients; set aside.
2Mix chili powder, cumin and garlic salt. Sprinkle mixture over both sides of beef.
3Place bell peppers and onion in grill basket. Cover and grill beef and vegetables 3 to 4 inches from medium heat about 5 minutes for medium-rare or about 7 minutes for medium; turn. Grill 5 to 7 minutes longer or until desired beef doneness.
4In large bowl, toss lettuce, grilled peppers and onion with half of the dressing. Cut beef diagonally into 1/2-inch slices; place on salad. Serve with remaining dressing, guacamole and sour cream.