They're filming something on Pershing, in the northbound lane just north of Imperial Ave in PDR. There's a silver SUV and a dark-haired girl. They have the cops out en masse to guard the orange cones on the road. I remember they filmed Entourage near this stretch of road last year, but I didn't see any of those guys. It could really be anything. Guesses?
Anyway, even if they're not filming anything interesting (if it is The OC I will never forgive myself), Pershing is the super-secret James Bond route around several miles of traffic on the 405. I've included a map. Remember who hooked you up with that shit. You're welcome.