VC22350 violation for unsafe speed but the no speed limit posted in the section of road where the violation took place?

I received a VC22350 violation for unsafe speed three months ago and finally just now received the materials for my discovery request. The material includes a copy of the officer's citation (w/ blank back page with no notes), the officer lidar training certificate, the calibration certificate, and road survey. The road survey was conducted more than 7 years ago but has recent evaluation that no significant change in condition had occurred. In the section of the road where the survey was conducted, there is no speed limit sign posted between the start of the section to the place where the violation occurred. The only posted sign is past where the officer was parked. If the unsafe determination is based solely on the prima facie speed limit, is no sign posted a viable defense?