It really depends on the snake...
I have most that don't mind handling from day-1 and have zero aggression whatsoever (all of those are in the same family as your cali king);
I have 1 that was tame when she was small and now you need to wear a harness to hold (one of the milksnakes);
I have 1 that always start biting when picked up but after a few strikes is calm like a sheep (one of the sandboas);
Some will always try to get the heck away (all of the milksnakes and sandboas
);
Some will really totally not bother with handling, even when eating or doing whatever.
I've learned my lesson though, because I do enjoy handling my snakes, though I do not enjoy when I know the animal is in distress because of it (and those I don't handle at all unless needed). So right now I do not purchase a new animal without prior handling (by myself). It still gives the best indications of the disposition of the animal..
Does the snake cling to you/hold on to you very tightly/feels very tensed up while holding it? It's afraid, it's going to take a while to get this animal comfortable, if at all... can still go either way though. It may help if you can hold its parents and see how they are.
If you hold you animal and it feels relaxed, it's going about it's business strolling around calmly exploring without tightly holding you, it's a very relaxed snake and not afraid of you or it's environment.
If it's musking, flicking around like mad, or striking at you, likely never going to calm down completely.
Also the snakes I have that are calm, are mostly out and about in their vivarium doing their snake thing (trashing stuff and pooping on my plants
). The ones that are afraid will hide 24x7 unless absolutely quiet.
Cali kings generally will be pretty great to handle (in my experience), but there are individuals that will not like it.