I'm at the Spectrum now and asked for you at Guest Services. They're not sure if overnight parking is permitted in the multi storey garages attached to the mall but they did say some venues here are open until 4am. I'm parked at 100 Spectrum Center Drive directly across the road in front of the mall. If you are visiting the Marriott over the weekend then parking is free from 5pm on Fridays and throughout Saturday and Sunday all day. There's no mention that you can't park overnight here from Friday evening onwards and I would not hesitate to do so. It's about a 10 min walk to the hotel. The parking garages at 200, 300 and 400 Spectrum Center Drive all charge $20 max daily. Hope this is helpful for you!