S.R.
I live in the San Gabriel valley. My neighbor had a firefighter bday party for her son last year. She got the truck to stop by her house. I think she just called up our local firehouse and asked if a couple guys could bring the truck over if they aren't doing anything else. As long as they arent on a call I think they are free to do that kinda thing. It was super impressive to the kids. The guys ran the siren and gave kids a look at a few things, then we took a picture in front of it. It was very cute. I think they stayed 10-15 minutes.
You should just call and ask. Or do what my neighbor probably did, which is walk over there with plates of treats, then ask :)