Cal. Civ. Code § 799.10

A resident may not be prohibited from displaying a political campaign sign relating to a candidate for election to public office or to the initiative, referendum, or recall process in the window or on the side of a manufactured home or mobilehome, or within the site on which the home is located or installed. The size of the face of a political sign may not exceed six square feet, and the sign may not be displayed in excess of a period of time from 90 days prior to an election to 15 days following the election, unless a local ordinance within the jurisdiction where the manufactured home or mobilehome subject to this article is located imposes a more restrictive period of time for the display of such a sign. In the event of a conflict between the provisions of this section and the provisions of Part 5 (commencing with Section 4000) of Division 4, relating to the size and display of political campaign signs, the provisions of this section shall prevail.