Astronomi-con held an event in dallas last year. From my understanding speaking to the organizers, they intend to hold one again this year. Dates for all Astro events are TBA still though. Last year they started in (edit:March) I believe, with Dallas in (edit:May).
edit: Just to add a little bit, the organizers are great guys. At least one of them has done playtesting for new rules for
GW over the years. These guys have been running events for a long time. The format is going to be different from most in the U.S. Overall it was a great experience when I played in their event in Winnipeg 2010 (marking my first big event experience). The organizers are great both at the event and then in a post-event hang out. The event plays out 6 games over 2 days. I can't promote enough how much fun this event was.