Cal. Streets and Highways Code § 889.2

(a) The department may install bicycle route signs, identifying bicycle routes of national, state, or regional significance, that are associated only with the state highway system, which includes state highways, United States highways, and interstate freeways, and state-financed public transportation systems. The physical placement of bicycle route signs on all other roads and transit systems shall be left to the appropriate local jurisdiction. However, when requested by a city or county and reimbursed, the department shall place bicycle route signs on the state highway system and state-financed public transportation systems that direct traffic to bicycle routes on city or county roads. (b) Bicycle route signs shall meet the standards and specifications established pursuant to Section 21400 of the Vehicle Code. (c) The cost to purchase, erect, and maintain bicycle route signs may be paid by applicants or nominating entities, as determined by the department. These costs may be reimbursed to the department at their actual cost, including administrative expenses.