funkapotamus, how do you figure everything around placerville is all "state land"? There's got to be lots of county land, city lands, and private lands. And since there are no restrictions on those, what's to stop you from merely hunting on spots you research out there, instead?
And if you wonder if there are rules at the other levels (county and city), the way to find out is to look it up for yourself. Nearly every municipal type entitity has a website nowadays. And as such, will have municipal codes, park rules, and so forth on there. If they say nothing about metal detecting (ie.: silent on the issue), then presto, it must not be disallowed. No need to ask any further questions.
And actually, as far as "state land", it's not truly 100% off-limits here. For example: state of CA beaches can be hunted till you're blue in the face, and no one cares. And the state beach system is administered by the same "parks system" that administers the in-land parks, right? And quite frankly, there are some inland state parks here too that have been detected, and it's not been a problem (so long as you're not a nuisance begging for attention, snooping around obvious historically sensitive monuments or something). Ie.: it depends on what ranger you ask (or if you even asked to begin with), and what his mood is, or what he even knows about the subject (as some just simply don't know, or don't register it when/if they see you, etc...).