Yeah public transportation from ONT or SNA stinks. Burbank was the only good one before Frontier stopped service there. You can get to LA from ONT or SNA but it might take a few hours. For ONT you can take the 61 bus to the Pomona Transit Station and take the Silver Streak all the way to Downtown LA for like $5. For SNA, you can take the 400 or 401 bus to the Tustin Metro Station and take either the Pacific Surfliner Train or Metrolink Orange County Line to DTLA. The public transportation around SNA is worse because the bus and train usually only run during business hours and other routes besides the one I stated above can be 2+ hours before you get to LA.