A sign shall not hereafter be erected, re-erected, constructed, and altered, except as provided by this code and after a permit for the same has been issued by the city. A separate permit shall be required for a sign or signs for each entity, and a separate permit shall be required for each group of signs on a single supporting structure. In addition, electrical permits shall be obtained for electric signs. All signs are subject to review by the building and planning departments of the City of Hood River.