Actually, I'd figure the rest of the month would still be a good time to go. This requires a pretty decent cross-country hike to get to, after all. If you can spare the time, I'd go for it. I'll definitely be heading back to do a multi-day trek through all of it. One day in is simply not enough.
I'm pretty much done with the travels this year. Just started backpacking this year so I'll keep that in mind. I scoped out a few this year from Island in the Sky down to the Green and Needles down to the Colorado. Fell in love with those rivers last year.