I just rode that section both down and back two weeks ago. At 65 years young, my fully loaded 950 ADV was a handfull. I think the worst section was from Hwy 1 to Coco's. Coco warned us that it was very rocky. I didn't find it scary or difficult, just had to keep the speed down and pick my way.
We found only one truly sandy section. Heading north from Coco's, it's an uphill turn to the right, immediately after a very short section of pavement (in the middle of nowhere
). I clocked it at 9 miles north of Coco's, 12.5 miles south of Gonzaga. The sand on the uphill (left side of road heading north) is very deep so be sure to stay way to the right. The road has become steeply banked so that won't be a problem when headed north. I hit the sand on our way south and ended up off the road in the cactus. Fortunately, kept the bike upright but it got my feeble heart going
I understand the cow incident Mark spoke of occured out on Hwy 1, near the Bahia de LA intersection. I don't think I could get enough speed up on the dirt section to tear the front off a GS
I'll be back down again next week so perhaps we'll cross paths. Be safe