Looking at the IxDA events on SL Design Week, and there doesn't look like there is anywhere to register for events... Is everything full?
Check out: http://www.meetup.com/IxDA-Utah/
All the events are posted there. Hope that helps. :)
The IxDA events at SL Design Week are free and first come. No registration required. For other events, I believe you register for the ones youre interested in directly from the events calendar.