Well that's not entiiiirely true... I've seen cars left overnight because the drivers were too drunk from Citywalk and had to take cabs back to their hotels. Officially you can't but I think 1 night is unofficially allowed because they would rather you not drive drunk.
Another option would be to park over near the partner hotels (by Friday's) and make the hike in to the resort. I guess it depends how much walking you want to do vs. how badly you want to save the money...