I think 'disagree' is far too strong. We simply stated our individual preferences. Tarheel said clearly that there might be other opinions. I made no mention of either your or Tarheel's version being incorrect. Neither did SD.So, it seems the two teachers who have responded so far disagree. Any way to resolve this?
That's English for you. I could make an argument for "across the valley" as well. Not "down across," but just "across." Or "along."
I would follow "down" with "into" if given the original choice. Cause it is entering, so "into" is more correct.