Went in where the People Mover drops you off..
Cobo garage was full by 10. Said park on the roof (entrance at 3rd and Congress). We had no idea where that was, so just parked at the Millender Center and took the People Mover over (yuck). Mill. Center garage is kinda creepy and confusing though. Paid $10 to park there. I'd just try to get there really early so you can park in the Cobo garage.