It's not too bad.
We either park in the parking garage or behind cirque du soleil. We don't try to find parking across the street or anywhere else.
Especially now that the bridge over the lake is open connecting near the
Lego store to rainforest cafe, it's not too bad of a walk to wherever you want to go.
I found the worst traffic to be during the weekends in the evening. So if possible I would go during the weekday. But DTD is nowhere near bad enough that it should deter people because of the construction