In my practice I am often asked "what is considered a "public place"?" (i.e., in terms of where the police can enter without a warrant, and whether you are considered in public under the definitions of certain misdemeanors like "public intoxication" and "minor in possession"). The following is an excerpt from the recent Krohn case (cited below) which gives some guidance on this case by case inquiry:
"The term “public place” generally means “a location readily accessible to all those who wish to go there … .” People v. Perez (1976) 64 Cal. App. 3d 297, 301. The key consideration is whether a member of the public can access the place “without challenge.” People v. Olson (1971) 18 Cal. App. 3d 592, 598. Thus, the Olson court considered a house's front yard to be a public place because “defendant, a complete stranger to [the homeowner], was able to walk through the outside area of her home to the front door without challenge.” In contrast, a location guarded by a fence or locked door is not readily accessible to the public, and is not a public place. In People v. White (1991) 227 Cal. App. 3d 886, the court refused to deem another house's front yard a public place because it was “surrounded by a three-and-a-half foot-high fence with a gate which was unlocked at the time.” (Id. at p. 892.) It noted “the fence, gate, and [three pet] dogs all provided challenge to public access.” (Ibid.) And an interior hallway of an apartment building was considered to be a public place because “[t]here were no locked gates or doors to keep the public from entering” it. (Perez, supra, 64 Cal. App. 3d at p. 301." People v. Krohn, (Cal. Ct. App. 2007) 149 Cal. App. 4th 1294, 1298-1299.
If you don't want random people, including police officers (whether you consider them "random" or not), snooping around your yard, balconies and other outdoor places on your property, and don't want you or your guest to be arrestable for public intoxication and/or minor in possession in these areas, you should enclose these areas with a fence. It doesn't have to be a tall fence, nor even locked, per White. Dogs and "No solicitors"/"No Trespassing" signs may present these legal cognizable "challenges" to unwanted intruders, however, it seems the only clear way to protect these areas from being considered a public place is to fence them in. I will say this: I'd feel more "challenged" by a rottweiler than a 3 and half foot fence.