Religious institutions, hospitals, nursing homes, private schools, service organizations and public buildings and facilities may have one (1) freestanding informal sign or bulletin board, not more than thirty-five (35) square feet in area, not to exceed six (6) feet in height, on each major street bordering the property, together with incidental signs, not to exceed four (4), necessary to provide directions or describe the use, provided that each such sign does not exceed three (3) square feet in area;