I have recently learned of case law cited in "Heller, High Water(mark)? Lower Courts and the New Right to Keep and Bear Arms" that indicates that this may not be allowed:
...the conclusion of a California court that a private drive was a “sensitive place,” thus bringing a conviction for carrying a concealed weapon under the Heller safe harbor,49 seems a stretch.
49. People v. Yarbrough, 86 Cal. Rptr. 3d 674, 682–83 (Cal. Ct. App. 2008) (rejecting challenge to conviction for carrying concealed weapon, and stating that “[t]reating as criminal defendant’s concealment of a firearm under his clothing on a residential driveway that was not closed off from the public and was populated with temporary occupants falls within the ‘historical tradition’ of prohibiting the carrying of dangerous weapons in publicly sensitive places”).
So, while the author of the paper seems to think that the California courts may be carrying the prohibition a little too far, it is valid case law, and it makes me cautious about carrying a weapon in my front yard, my driveway, or even inside my garage when the garage door is open. I don't know about my backyard, but this is California after all.