I think you better have a box upstairs and downstairs both, a puppy will quite often wait till the last second before even thinking of looking for where they should go (a lot like small children, LOL) and if the puppy is downstairs a lot I think you can expect accidents without someplace for it to go. We take Marcus everywhere and he travels in his crate so the stores and restaurants he can't go in he waits in his crate and he's never resented it. It's got his blanket and toys and he feels content to wait till we get back. I don't crate him at home but the crate sits on the floor close to where we are and sometimes he crates himself if we are too busy to let him sit on a lap. He sleeps with us and at first when he was very young we would get up a couple of times a night to let him use his pee pad. Now he licks my face to let me know he's got to go but I'm seriously thinking about getting a ramp like Kemo's Mom got so he can get up and down by himself.