Just an update, this group is still going VERY strong over 2 years later :)
It's still a very casual and social group - no set topics or mandatory attendance; show up and leave whenever you like, grab a coffee or sandwich and just chat with fellow atheists/agnostics/etc.
We still have new members showing up almost every week, typically 10-15 people engaged in a few casual conversations at our Sunday meetup. Some members take a more active approach and organize debates or events on the side.
Note, original facebook page is defunct, our main one is here:
Meetup page is still valid and where all of our organized events are posted:
Hope to see you there!