>All else being equal, would you rather eat a hot dog from a cart with a nice sign, or from a guy sitting on the sidewalk who sharpied "Hotdog $3" on a piece of cardboard?

You keep introducing these silly confounding variables. I wouldn't eat from any hotdog vendor who is sitting on the sidewalk, regardless of their signage. If both had carts, the signage wouldn't affect my decision, particularly because hotdogs are shit in my opinion. As nice sign on a hotdog cart is like putting lipstick on a pig.