This trip report could be of interest to a climber. One possible objective is the spire pictured above, located a short distance up Grand Gulch. You’ve already done all the swift-water sections by the time you get to Grand Gulch. The crux may be the logistics, as you are only allowed one night camping at a given [assigned] site in this section of the canyon. There are amazing bouldering opportunities, as well as some high quality limestone right along the river.
Spring break 2019. We had a lot of rain recently, and the river had spiked up to 6000 cfs just a few days prior to my trip. By this time, though the flow had subsided to a more normal 1,300 - 1,400 cfs. However, more rain was in the forecast. I was putting in at Mexican Hat on Tuesday, planning on 3 days to do the 56 miles to Clay Hills crossing. Rain was predicted for Wednesday night. I thought I'd see just how far I could get in a day, and maybe do it in two days to avoid camping in the rain. Plus there were several washes crossing the road to the take-out which I'd rather not cross when flowing.
On the first rapid, Gypsum Creek rapid right outside Mexican Hat, a wave train going through a corner. I got stuck on a rock at the top of the rapid. I had no choice but to get out of the boat and muscle it off the damn rock. This is actually possible on most parts of the San Juan at average water flow. That was a little sketchy! There isn't any real serious whitewater on the San Juan, but it does have a few in the class 3 range. Gypsum Creek wasn't one of the ones I thought I had to worry about. Government Rapid is the big one on this section, but Ross rapid, John's Canyon rapid, and one other rapid were worth getting out and scouting before committing. I followed the River Ranger through Ross rapid and so avoided scouting it, but you should.
I was able to make 30 solid miles, paddling from about 9:00 AM to 5:30 PM. I passed a few parties with big oar rigs, I was definitely moving faster than they were. The weather over night was beautiful, full moon and all! The second day found me nervous about the upcoming rapids. I had pretty much decided to try to paddle all the way to the truck today to avoid the incoming storm.
Once I got on the water I just clicked in to go mode.

John's Canyon rapid was fun as hell, a classic wave train that goes on for a ways. Another rapid I was able to hug a rock wall for a straight shot on river left. I don't know what the rafters would do on that one, I don't think they would fit the way I went. Government rapid was heads up, but also pretty much a straight shot to avoid the rocks and holes. No problems.
I was at Slickhorn Canyon by lunch time. That marks the end of the rapids. Lake Powell backed all the way up to Slickhorn Canyon in 1983 - 1984, apparently depositing up to 40 feet of sediment on top of the original river channel. Needless to say, this bottom section, while scenic, was slow going. A raft would have required a lot of dragging through quick sand - not fun. I would not recommend doing this section under 1,500 cfs.
I did the 26 miles in about the same amount of time as the previous day's 30, made it to take out by 5:30, drove to Blanding for a bacon guacamole burger at the Patio Diner (simply the BEST), and slept in a cozy hotel room through the horrendous rain storm. Yes!