SMITHERS, where are you going hiking/camping??
I lived in Los Angeles for 35 years, and have done a lot of hunting, camping, hiking, fishing, in the State.
At this time of the year, the very long odds are you'll not have to worry about rattlesnakes (the only poisonous snake in Calif., other than a rare few Coral snakes down along the s.e. Calif. border with Mexico/Arizona). Late Spring, Summer, and early Fall are different stories!
As for a rifle, plenty of advice here but I'll offer mine, anyway. Get a Ruger 10/22 and four extra Ruger factory ten round magazines. You can do a lot of shooting over the years with that reliable rifle. I've carried mine for many a mile and barely noticed the weight. Bought it new in 1979 and it still runs like a fine Swiss watch.
As for Calif. laws, if I were you, I'd go buy a Calif. Hunting License, as you then have some leeway in carrying a firearm in the Nat'l. Forests, Wilderness, and State Forests. (Firearms are forbidden in Calif. State and Nat'l. Parks.)
Get a copy of the Calif. Game & Fish laws and read them, especially the section regarding firearms. Renew that Hunting License each year.
Not to say you should not be attentive to the possibility of bears and Mountain lions, but again, long odds, you'll have no trouble with them.
In my opinion, your main concern will to watch for the two legged predators. There are definitely some out there in the boonies.
You can carry a handgun OPENLY if you wish, out in the boonies. I did for 35 years and was never questioned on it.
Good luck.
L.W.