bk,
The regs say.....If the property doesn't belong to you, it belongs to someone else.....It is your responsibility to know who that is.....Be it the state, the feds, corporation, or a person.....With that said....Legally in a court of law, it should be posted 3 signs to the mile, cultivated, or fenced.....So what that means is, you could probably hunt it and get away with it.
This day & age with OnxMaps, it will tell you who owns it.....No reason to not own this app in SoCal.
ps....I once got a trespassing ticket while hunting.....The warden said I was on private property.....Yet the signs were south of where I was standing (no fence or cultivation either).....To the north of the signs was national forest.....He said that their property went up to the NF signs (1 sign stating must be in legal pursuit of game above me)....There were no signs between me and those signs.....Needless to say, I went to court and beat it easily.....The point being here is, you just don't know what law enforcement will determine despite thinking you do know who owns the land. That's why it's important to know the legal aspect of trespassing.