No sign shall hereafter be erected, re-erected, constructed, enlarged or altered without a sign permit. No sign permit shall be issued except as shown on an approved site development plan or sign plan. Where only the sign display portion of a validly erected sign is being changed, no sign permit is required. Signs conforming to the New York State Department of Transportation Manual of Uniform Traffic Control Devices, and other traffic regulatory signs shown on an approved site development plan or required pursuant to the order of municipal traffic control agencies, shall be exempt from the requirement for sign permits. Political and temporary signs as provided for in Chapter 223, Signs, Article I, Temporary Signs, of the Code of the Town of Ramapo shall comply with the provisions of said chapter.