Should you plea guilty to turning on no turn on red sign?

If the cops have concrete evidence of your violation, it's best to plead guilty in a sincere manner. Avoid transferring responsibility. As long as you show understanding of your violation and remorse for committing it, then you can generally plead guilty and get out of it by taking a driving course.

Added: Before you plead anything to a traffic offense, you should check with your state's DMV for their point system. You will want to know how this offense will look on your record. Pleading guilty does not "get you out of it." Pleading guilty is accepting all consequences. Some courts will offer a reduction in exchange for driving school or other considerations, which may help keep your record clear. You should go to court or talk to a lawyer to find out if this is available, even if you are actually guilty.