In a situation like that, if it's a busy intersection. I would do a box-turn.

...In bicycling, the box turn is what you do when you make a left turn by going straight across an intersection, turning sharply at the opposite corner then crossing again. A picture is worth a thousand words, so I drew the box turn in pink in the diagram below

ref: http://www.cyclelicio.us/2011/box-turn/

You can get other advice at http://www.bikexprt.com/streetsmarts/usa/index.htm
also on YouTube they have good videos at the "Cyclist eye view". http://www.youtube.com/watch?v=ZFjCza5e1kw