Honestly I wouldn t be wandering around the Santa Monica area after mid-night...But if you insist, check the south eastern horizon 12 to 5 am.....at the darkest place you can get to...
The problem with the whole LA metro area is the light pollution. Even if you re able to get a campsite at Leo Carrillo State Beach or down at Doheny State Beach, you re still close to the LA metro area. We always tell people to get out to the desert for the best viewing. But if you can t, then try the beaches mentioned above, or go further north to McGrath, Carpinteria, El Capitan, or Refugio State Beach. You can get a campsite and stay all night. Lake Cachuma in Santa Barbara County should be OK, too.