And probably a half-dozen times before. Not much in the way of artifacts there outside of the old Emigrant Road. There is absolutely a ton of stuff on Comb the other side of the road worth looking at.
Should point out that at less than a 1000 CFS, the Comb Ridge campsite is inaccessible from the river. It's filled in a lot the last 2-3 years plus it seems to have an increase in ATV/OVR usage although it's always been visited via the wash. If hiking the wash or ridge, it's usually the best access point.
Have quite a bit of upper canyon information at my web site from previous trips, but this TR might be in line with what you are looking to do:
San Juan River - April 24, 2006 - Sand Island to Mexican Hat