There are no strict rules at all :-). I strongly encourage that food brought to share with the group be paleo-friendly, but you can do whatever, and certainly you can eat whatever you want yourself.
OK, I was feeling very conflicted on this, until I realized this might just be an inferential distance thing. I tried to clarify my confusion....and realized: I am not sure why the encouragement to bring paleo-diet exists. Do you assume most people attending would keep to paleo-diet? (That's not my model, but perhaps I'm wrong) Do you want to encourage people to try paleo-diet? If so, is it because you assume most people haven't tried it, and would subscribe if they tried it?
I'm sorry to be a pain about this...but I think we should be, at the very least, able to discuss snacks at a less wrong meet-up in a rational way :)
Shannon and I are going to be hosting South Bay Less Wrong meetups at the Tortuga community in Mountain View on Thursday nights starting at 7. Come prepared to reveal something you're consistently irrational about. We'll spend some time throwing ideas around and then hang out and mingle.
Bringing paleo-friendly food is a bonus but not required.
If you'd like to come, request an invitation from our google group, Tortuga Rationalists.