It wasn't that Dean couldn't use a talk about Sam, Hell, and everything else. It was that there was no good reason he could see right this second to make Jo think about all of that. There were more immediate problems. Like flying for no reason. Like the Tunnel of Terror actually producing terror without the aid of fake plastic ghouls.
"Sam's..." Dean shook his head. He hugged Jo, and gladly, when she put her arms around him. "Sam's gonna have to wait."
It sounded cold, but it was true. If York was imploding because of the fair, even a little bit, that had to be worked on first. There were a few thousand people in the York area.
Sam was just one person. Even if it was his brother.