Approximately two hours from LAX to Bakersfield, by way of the 405/5/99. Oddly enough, I'm making almost that exact drive tonight (but, I'm heading to Buttonwillow on the 5, instead of Bakersfield on the 99)...
Your time of day should work out pretty well for you. Shouldn't be too much traffic then. Maybe some lunchtime rush on the 405, but it shouldn't be horrible.