Sans shrugs, an automatic response, and then adds a little nonchalant "eh" in there when he remembers Arthur can't see that. "Figuring out how I'm supposed to act I can probably do, but if there's anything you think might be super important, hit me."

He doesn't know what happens if you stand out here, but his natural paranoia, the knowledge that he's really a monster among humans, means he's inclined to keep his impression to "weird human" and nothing else.