I don't recall my Montana avoiding left turns at all. Now I'll have to go out and test. Could it be something that changed since version 5.40 on the Montana 650? (Wait. 7.60 is over a year old? I'm still living in 2013? Well, it works for me.) I would think that "avoid left turns" could be easily added to the avoidances preferences. But then we can all think of features that someone else should add to the code.