If I go to the unsubscribe button for spam mail, am I inadvertently signing myself up for more spam?

It depends on the source. I've bought various things online and gotten emails from the established company that sold to me. Those unsubscribe links tend to work. But if it's true unsolicited spam from a mysterious source, I doubt unsubscribe will work. For me, gmail has been really good at filtering out true unsolicited spam.