For what it's worth, I drove up to Anaheim last night to visit Trader Sam's and traffic was pretty heavy, both on the freeways and in the resort. The DD parking lots were full and they were diverting traffic away to other areas. Interestingly, Sam's itself was NOT super busy. Able to get seats at the bar all night.
I would think traffic will be ok until late morning on Thursday. People will then start going out. Not super light, but not gridlocked. If you're driving to DLR on Thursday, I'd think the eariler you got there, the better.