Min age for OC is 18. National forest is ok for OC. The train, you might want to check their rules from their site. Private property can post no firearms, but signs have no force of law. If they ask you to leave, leave. Don't want a trespass charge.
Forgot: Parks and Wildlife is a hit or miss. Those guys are a little different from the standard LEO. Sort of like giving the mall cop a gun and telling him to watch the grass. A lot are great. Some, just a touch off. The one and only time I've ever been harassed for OC was by a P&W officer in Conifer. He went out of his way to inform me that I should consider the other people around me and maybe not OC. I informed him "I'm good." BTW, we were in a Qdoba, not in the forest and he went out of his way to approach me and lecture me about OC. I'd been in the place 10 minutes before him and no one else even cared.