This is sort a follow-up to this thread.

I found that DRLs can burn out your ballasts. However, I have an 06, and I'm told that the marker lights do not count as DRLs, and GM switched to low beams on 07s. Does that mean that I don't have to do anything to the fuse box on mine?

 

Correct, 05-06 lack the DRL fuse.

 

so it's safe to leave them on automatic? or should I just turn them on and off manually?

 

ya your safe. The auto lights aren't going to hurt anything. Nor will having the parking lights as DRLs.