Stop by, becasue you want them to come by and say hi or something but when you say "bye" it's as if they are leaving so you are saying good bye to them
If you mean "do they," I would say rarely. I see bicyclists blow through stop signs all the time. If you mean, "Are cyclists required to obey traffic signs," the answer is yes. Cyclists are required...
stop giving it water and/or foodyeast will also kill itself by fermentation; in a closed system the yeast will consume all it's food resources and produce enough alcohol to kill all the yeast cells.