The fact that you have an upcoming left turn is less significant, IMO, than the fact that as slow traffic you're required (and more importantly, expected) to keep to the right. Taking the left lane at an intersection is not expected behavior for cyclists, and the key to safety is to never take drivers by surprise.

It may not even be legal, depending (probably) on exactly how far down your left turn is.

I would stay right, and do whatever seems safe. If the pack passees me between the time we all start from the green and the time I approached the turn, I'd then simply merge left and make my turn. Otherwise, I'd stop at my turn and wait for the light to change.

RichC