After I got my first ticket, I talked with a friend of mine who is a retired cop, among other people. Here are the general rules:
0-5 over:
You're almost certainly not going to get pulled over in this range. Of course, now that I've said it, someone is going to post "OMG this asshole cop gave me a ticket for 3 over", but I've never heard of it.
6-14 over:
Most cops won't take the effort of pulling out and chasing you down in this range unless a) the speed limit is under 35, b) its a residental area, or c) you're making yourself a very high profile target (see below)
15+ over:
You're toast.
High-profile targets:
Passing on right or driving constantly in left lane
Out-of-state plates
"Leading the pack" - first car up is most likely to feel the radar gun.
Sports cars
Red/black cars (statistically more likely to get tickets)
In VA, 80 or more is reckless driving in a 65 zone, and 60 or more is reckless in a 35 zone. I'm not sure what the CA laws are, but when you get a ticket for reckless driving in VA, the cop can arrest you at his/her discretion, and if they let you go they inform you that you HAVE to go to court and CANNOT prepay the ticket.
Driving education classes typically are limited to those under a certain number of mph over the limit, and I can guarantee you exceeded it. Go in and beg for mercy.
Edit: By the way, 20 mph over the limit is about a $1500 hike in your yearly insurance. 25 mph is going to hurt even worse. Plead with the judge to knock it down a few mph. If you were polite to the cop and take the time to go to court, they'll show you some mercy.