Let me give you a perspective from a somewhat "shy" couple. We're both very friendly, very outgoing people, but when we go to clubs (not many house parties in our area), we do tend to be a bit shy and reserved. Just our nature. We would actually welcome having someone come up and say hi or introduce us around. Once we get going, we do great...just have trouble getting started. So our vote is to definitely extend your hospitality to us 'wallflowers' -- you never know how we may repay the favor