As a reminder here are the Las Vegas Strip properties owned by MGM: Aria, Bellagio, Cosmopolitan, Vdara, MGM Grand, Mandalay Bay, Delano, New York New York, Park MGM, NoMad, Luxor and Excalibur.
MGM Resorts International owns many of the most famous Las Vegas Strip casinos and unfortunately you will pay for both valet and self-parking at all of them. How to Avoid Paid Parking at MGM Resorts Properties in Las Vegas