A.   Streets With Signs: When appropriate street signs giving notice of the maximum permitted speed thereon are erected, the prima facie speed limits designated upon said signs shall apply to the appropriate streets or portions of streets so posted.
   B.   Streets Not Posted: Unless otherwise provided in this chapter or in any other ordinance of the City, the prima facie speed limits on the streets of the City shall be twenty five (25) miles per hour. (1982 Code § 11-323)