California Code, Civil Code - CIV § 799.46

At the entry to a recreational vehicle park, or within the separate designated section for recreational vehicles within a mobilehome park, there shall be displayed in plain view on the property a sign indicating that the recreational vehicle may be removed from the premises for the reasons specified in Sections 799.22and 1866 and containing the telephone number of the local traffic law enforcement agency.  Nothing in this section shall prevent management from additionally displaying the sign in other locations within the park.