In another large bowl whisk together the next 9 ingredients(mayonnaise, sour cream, spicy salsa, milk, Cajun spice, parsley, hot sauce, dill weed, and cumin), cover, and chill until needed.
Grill the marinated chicken breasts for 3-5 minutes per side, or until cooked through. Discard leftover marinade.
Brush grilled chicken with reserved dressing, sprinkle with cheese, and broil until cheese has melted.