I wouldnt mail in anything till they request you do so.
I dont live in CAli, but in Indy 12mph over is considered wreckless driving and is usually permanent dings on your driving record. Unlike tickets usualy drop off after a few years.
Expect to pay out the ass on fines and insurance.
Lastly take it to traffic court and fight it. Maybe you can get it droped down to lesser speed/ticket.
Good Luck !