can you wear it outside of your coat?

As far as I know, open carry isn't expressly forbidden in Montana unless you are in certain buildings. But I'd contact the police to find out the most recent laws. Why do you want to do this anyway?

I'm sure it's got something stupid to do with either undocumented immigrants, documented liberals, or both.

You can wear it unconcealed unless a city ordinance says otherwise. You can't wear it where alcohol is served or government buildings, banks, schools etc. You can go online and find all the rules.