OK, stop right there...
Here is 22450:
(a) The driver of any vehicle approaching a stop sign at the entrance to, or within, an intersection shall stop at a limit line, if marked, otherwise before entering the crosswalk on the near side of the intersection.
If there is no limit line or crosswalk, the driver shall stop at the entrance to the intersecting roadway.
(b) The driver of a vehicle approaching a stop sign at a railroad grade crossing shall stop at a limit line, if marked, otherwise before crossing the first track or entrance to the railroad grade crossing.
(c) Notwithstanding any other provision of law, a local authority may adopt rules and regulations by ordinance or resolution providing for the placement of a stop sign at any location on a highway under its jurisdiction where the stop sign would enhance traffic safety.
With what you said, the underlined part is the reason why the officer cited you; simply because you stopped not at, not before, but past the limit line.
Traffic school is automatically available to you at the outset, if you opt for a TBD or a trial, there is no guarantee that the judge will allow you that option after.
I can see the stop sign fine. even from that distance. Even if it was covered in the picture, those images appear to be from 2007. Who knows what the trees look like 5 years later in 2012.
Your claim that you were going downhill and/or at night has no basis as a defense. As I don't see those exceptions in the code section! The sign is not obstructed by trees or anything else. And assuming you were using your headlights, the sign is made with reflective paint which makes it glow at night. Additionally, you stopped... So your claim that you did not see the sign does not make sense! And lastly, even if you did not see the sign, you should have seen the limit line as well as the STOP marking painted on the pavement.
You've got so many things working against you and the officer hasn't even testified here. You'd have no chance to beat this on merit!
Good luck anyways!