Some of our bus passengers will be staying with friends and family outside of downtown. If you are driving to Millennium Park (most of us will be cabbing it), the link below has information on parking:
http://millenniumpark.org/generalinformation/directions_parking.html
I just called the lot. The garage is open 24 hours, and fare for 14 hours (I was told) would be $16. That is outraegously cheap for downtown Chicago parking!