COOK spaghetti in large saucepan as directed on package.
MEANWHILE, heat dressing in large nonstick skillet on medium-high heat. Add chicken and garlic; stir-fry 3 min. or until chicken is no longer pink. Add peppers, onions, broth and peanut butter; stir-fry 3 to 4 min. or until chicken is done.
DRAIN spaghetti; return to pan. Add chicken mixture and soy sauce; mix well. Spoon onto platter; sprinkle with cilantro and nuts.