I commute from Long Beach to Downtown LA (22 miles) twice a week...next week I'll start doing it three times. I'm no speed demon, so it takes me about 1.5 hours.

I take the LA River to Vernon and ride the last 6ish miles in the street.

I'm originally from NYC. I don't see many commuters on bike, which is a surprise because the weather is great most of the year in LA. I'm guessing the car culture plays more than a small role here.