I would go back again a few more times. People are diffrent. Some people find it hard to talk to someone they don't know while others find it really easy. Some people need someone to come in between their little twosome or threesome so by going a few more times they will get to know you and you will better be able to assess the group. Go to the other guild also with the same itinerary and see where you feel the most comfortable. Maybe you will join both or maybe none but at least you would have given it a honest try.
Good luck.