Cal. PCC § 20150.7

The notice inviting informal bids shall be by published notice and may, in addition, be supplemented by mailed notice to contractors registered pursuant to Section 20150.6. The county may cause the notice to be printed as display advertising in such form and style as it deems appropriate. The notice shall describe in general terms the project to be done and state a closing date for submission of such informal bids. Publication of notice pursuant to this section shall be in a newspaper of general circulation printed and published within the jurisdiction of the county, or, if there is no such newspaper within the jurisdiction of the county, publication shall be made in a newspaper of general circulation which is circulated in the jurisdiction of the county, or, if there is no such publication, the notice shall be posted in at least three public places within the jurisdiction of the county as have been designated by ordinance or regulation of such county as places for the posting of its notices. Notice shall be published in accordance with Section 6061 of the Government Code and shall be completed at least 24 hours before the time scheduled for opening of the bids.

In addition to notice published in a newspaper of general circulation, mailed, or posted, pursuant to this section, the county may also publish notice inviting bids in a trade publication.