If there was no stop sign in place at the intersection, the defendant should be acquitted. It is an element of the offense that a stop sign must be present. The fact that the rules for inoperative signals are the same as a stop sign in this case is completely irrelevant.
I would suggest TBWD with photos demonstrating that the offense was not committed. This is better than an in court trial for at least two reasons. First, there is no opportunity to amend the charge, at least if the court follows CRC 4.210. Second, the officer is not looking stupid in open court. Some judges will amend, delay, or dance around before they will make an officer look stupid.
As I usually do, I'd suggest delaying the process as long as possible, unless the defendant can't keep track of dates and time frames.

