I'm also pretty sure you can attend any chapter's meeting, without actually being a member. They usually just ask if there are any new people present and if they would like to introduce themselves. I've been to meetings of all three chapters and enjoyed all of them.
If a chapter is becoming stangnate, maybe a dose of fresh blood would be good for it. I guess it depends on how much you want to contribute. We all need extra help.
Everyone can help in some way.