The fact that she mentioned Dean did nothing to ease the tension that Sam immediately found plaguing him at the sight of her. Mouth twisting into a frown, Sam dropped his gaze to the spot on the floor that was hidden from Jo by the door. The trap mat that he'd created was there, only a few inches off from where she was standing. If she was able to actually cross the space without any trouble, he'd be more comfortable with her presence. Until then...Sam tilted his chin upward, eyes dropped down to examine Jo with an air of uncertainty. She was claiming to be acquainted with Dean. In a friendly way. And if she actually had salt on her person, then she clearly wasn't an actual demon. But since Sam couldn't exactly see the salt out in the open, as Jo had it (or something) tucked away inside her bag, Sam didn't want to make any sort of foolish assumptions. He wanted to be safe.
"Yeah," Sam said, biting back the frown that had briefly over taken his features, "yeah, you can come in. Hang on." Pushing the door shut, Sam stooped over to drag the trap directly in front of the doorway. As soon as she stepped inside, she'd land right in the trap. Easy enough, wasn't it? Once it was perfectly aligned with the door, Sam placed a large hand on the doorknob and carefully pulled it open. Stepping aside, he gestured for her to come in. "You can put the salt on the bed there." Sam didn't say anything else. He didn't ask her what her name was, nor did he bother attempting any formalities. Until he was certain on who - or what - he was dealing with, Sam didn't want to bother playing nice. Because if she really was a demon? Attempting civility would have been an absolute waste of his time.