My guess is that traffic flows more or less equally in both directions. Worst is to go with the sun low in the sky - you will have it either in your eyes or blinding you from the rear view mirror. The public buses run equally in both directions. Tour buses may go in either direction and stop in several towns along the way, so there will be buses eastbound and westbound throughout the day, as well as local and tourist cars - and probably lots of motorcycles and possibly some bicycles too. It will be challenging to pull over to park for pictures in either direction, because other cars will have parked in all or almost all the possible places ahead of you. Also allow plenty of time to find parking if you want to stop at any of the towns along the way.
Also be prepared to go very slowly. For the most part, buses stop in the road for passengers (there are very few places for the to pull off the road. And when buses meet other buses or large vehicles at sharp curves, it may take quite a while until one side backs up (the large vehicles know who should back up - but it can take a long time for all the cars behind it to figure out they have to back up). The one thing you probably won't have to worry about is taking curves too quickly - chances are you won't be going very fast.
I drove back and forth twice in February when there is virtually no traffic on the road, I never went above 50 kph, was usually at around 35 kph and often at 20 or less.