The County Building Code is online here:
http://www.co.san-bernardino.ca.us/landuseservices/devcode/806-Planning%20Areas%20and%20Specific%20Plans.pdfOn page 6-79, it states:
(5) Open fences not to exceed four (4) feet in height shall be
permitted within a required front yard area. For purposes of this
section an open fence shall mean those types that are
composed of wire mesh or wrought iron capable of admitting at
least 90 percent of light.
(6) Solid fences and walls not to exceed six (6) feet in height shall be permitted along side and rear property lines except that no solid fence or wall exceeding three (3) feet in height shall be
located within any required front yard area.
(7) Open fences as defined in subsection (5) above that are over six (6) feet in height may be located in the rear half of the lot subject to a finding by the reviewing agency that such a fence will not constitute a nuisance to abutting property owners. Such fences up to sixteen (16) feet in height located within the buildable rear yard area of a lot and not less than ten (10) feet from any property line are exempt from the requirement.
My read is that Open (i.e. chain link) fences 4 ft or lower are per code, otherwise a varience is needed.