pdykstra600
Go Kart Champion
Aren't traffic tickets strict liability? I don't think you are best served by arguing that 80mph is actually safe.
In most states, yes, speed limits are absolute (per se). Arguing that 80 in a 70 was safe for the conditions would mean that you are guilty of speeding, because the 70 mph limit is set by statute and you are automatically guilty if you go over it, even if you were driving safely.
There are some states that have prima facie speed limits. In those jurisdictions, you can actually argue that your speed was safe for the conditions even though you were driving over the limit. If you could successfully show that your speed was safe, you would be not guilty of speeding.
No idea what the rules are in California, but you'd better find out before you send in that letter.