[Pazuzu]

Not a Cali resident, but I don't think that matters here.

The problem is a question of escalation. Yes, calling the cops is one option, but it escalates things too far too quickly.
I would do one of two things...either walk into the establishment and alert the management there that one of their patrons has a dog in the car, and could they please talk to them, or ask if *I* could talk to them. Even if it meant standing there and yelling "hey, who left their dog in the car to die!". What, the person gets horribly embarrassed? Fine, at least they go fix the problem. The police option involves someone being embarrassed, AND getting fined/jailed, AND taking officers off the beat to deal with something that could be solved without them. Too much escalation too quickly for the incident.