I'm in Northern California, and the picture changes pretty radically depending upon which department you are dealing with. The Sheriff's deputies I know are pretty vocal about the fact that they are (mostly) grateful when an armed citizen offers assistance. This is likely because they cover a wide territory and are often on calls alone. Backup is far away. It also has something to do with the fact that they actively court a positive relationship with hunters and CCW carriers.
Some of the local PD are less inclined towards any citizen involvement, and actively dissuade it. I imagine this has to do with the fact that uniformed backup is usually pretty close by.