Is the San Juan worth traveling another 50 miles? Huh.....
YES. This one was taken a week and a half ago by me, on a black ant pattern (yes dry flies work when you have the right one presented properly to feeding fish. This is the most active time of year for terrestrials).
This fish is representative of an average SAn juan fish, not even a big one.
With an estimated 20,000 trout per mile, the SJ is one of the most fertile rivers in the US.
With an average fish size of 17," the San Juan has some of the largest fish in the US. 30" Rainbows and slightly smaller brown trout are not unheard of.
The San Juan is no secret, so it will be crowded and during the summer fairly hot. You also might run into a lot of stockers, they put them in by the thousands and they grow to 16" within a year.
This fish was taken while wading. it is not necessary to float the river unles you really want to be guided and hook into even bigger trout.
Other options (for big fish): The Animas through Durango is an excellent river.