I've heard of open days at Laguna... but only once or twice since including them in the TDR schedule (around 2007).
My observation is that big tracks like this tend to do fewer "open" days because they're filling their calendars far in advance. Maybe one of the club organizers can share their thoughts on this.
Check their calendar often. If you find any, be sure to post back here!
http://www.mazdaraceway.com/pages/Track_Calendar_2010