We've had 544 and 546 facing Epcot. Same story -- no road noise if balcony door closed, and not all that bad even when it's open.
There isn't a lot of traffic since no one HAS to use that section of road. Only reason to go that way is vehicles going directly from S/D, YC, or BC to Boardwalk, or vice versa. And BC/BCV guests who realize that it's actually quicker to ...... oops, forget I said that!
I think it would be worst in a 1st or 2nd floor room near the end of the building.