That happened to us today at DHS. We got there at 6:30am and no one was there at the booths but the green light on the booth was on and no cones. So we just went in and parked. Walked over to the Boardwalk bakery for a snack and walked back. I asked a security guard when we got back if it was ok and he said yes that as long as you find a spot you like, are parked in between the lines and not parked in a handicapped spot if you don't qualify your fine.
Just figured I'd ask cause I was expecting the MK to be more tight on having you wait until a certain hour before letting you park.