Sorry to stray off topic a bit but that is really interesting and sounds like it could be a great learning experience and just interesting to see how they work and everything. Can anyone do this? Would you just have to call the department and ask what their policies for ride-a-longs are? Is it the same process to get one with a fire department?
Call your local law enforcement agency and ask them. They will advise if they have such a program or not and the rules/conditions for doing so are. Be prepared to sign your life away. Most agencies I am familure with have a wavier you will have to sign basicly stating that if you get killed/injured you family can't sue. (Not real sure how it would stand up in court, but we use one. It's never been tested to my knowledge)
You will probably have to be 18 years of age. DO NOT show up with a camera unless you clear it with that department first. It can be a real eye opener for people that have never truely seen how law enforcement works. Nothing like the T.V. shows make out.
As for riding with the fire department, I do not know if they have such a thing. They function in an entirely different manner and may not have the capacity for a ride-a-long. You would just have to check it out and see.