Each city is a little different, some are very strict regarding open house and real estate signs. We do not want anyone to lose their valuable signage. The city ordinance is the best guide for deciphering whether or not you need a permit in that area, NOT if another agent has held an open house in the area and didn’t have signs picked up.
In general, it's best to ALWAYS check the details for the city you will be holding an open house in advance so that you are able to get your permit in time.