I go along with much of what has been said. RegularGuy and MichaelW hit pretty close to my way of thinking. Exposure bad. I approach left turns in one of three ways.

1. Quiet road, make the left.

2. Busy road, don't even get in the left lane. Stay right and pull off the road. Wait for clearance both ways then cross 90 degrees. Yes, sometimes you might wait a long time, but it beats being roadkill. The thing is, you can't get in the left lane THEN decide it's too busy and change your mind. You have to stay right from the beginning.

3. If the street onto which I need to turn left is a quiet street I will take a right, U-turn then cross straight, again, even if it means a longer wait. My attitude about time is "If I were in a hurry I wouldn't be riding a bike."

Rainman's first rule of cycling: "Arrive alive." All else is secondary.