my underage friends and I were playing a drinking game outside but not within view of any public property, only in view if you walk significantly deep in the apartment complex. The cops sneak up in street clothes and unzip their jackets to reveal that they are the police and write us up
If it was in SLO City … maybe. Laws on possessing alcohol in public tend to be set at the city level, so it varies from city to city. Some cities restrict drinking in the front yard to places totally behind a fence. Other cities, have no open container in public laws. SLO is somewhere in between, as I understand it. So it kind of depends on the layout of the apartment complex – whether that part was open to the public. But the government has the burden of proof. If you’re not certain you did the thing you’re accused of, you can set the matter for a hearing. Hearings in infraction matters are quick and you can self-represent.

It is unlawful for any person to have in his or her possession on his or her person, while on any city street, sidewalk, alley, roadway, parking lot, publicly maintained place or any place open to the public any bottle, can or other container or receptacle, containing any alcoholic beverage which has been opened, or a seal broken, or the contents of which have been partially removed, or to consume alcoholic beverages while in the above restricted areas. (Ord. 1070 § 1 Ex. A (part), 1986: prior code § 4600)