I'm checking multiple times a day, but have not heard any leaks about the location as yet. As of now, I stand by my original SWAG, of Laguna Beach (most scenic IMO) or Dana Point (more room there to stage a small fleet of C8s that could take select reporters up to the VERY twisty Ortega Highway to show off the handling.
I was born in Santa Monica and as a teenager lived in OC and cruised Whittier Blvd and surfed at Huntington Beach (sometimes on the same day). I KNOW OC. We no longer even have a drag strip, much less a race track. At one time the closed El Toro Marine Air Base landing strips were used extensively as a test track for TV Car shows, but it is now deep into its conversion to housing tracts and parks.
The Anaheim Convention Center (across the street from D-land) is BIG, but no place to test drive a C8. The Angels' Big A stadium parking lot is huge but there is a game that night and why debut there? It's not a pretty area, nothing special. It's not far from D-land and the streets are pretty busy.
I am working with DC Admin hoping to wrangle an invitation to the debut from GM. It's a very long, long, long shot that this could happen, but I can guarantee you that on 7/17/19 and 7/18/19, I will be driving my C6 up and down Pacific Coast highway looking for any indication of a debut site...unless we hear more before then.