Just so you all know, getting to the bottom of Rattlesnake Canyon is not all that tough - some boulder scrambling to do, but not all that long of a hike. Rattlesnake Canyon is supposedly the only slot canyon in Joshua Tree Park. The little creek has carved out the slot in the rocks - difficult to shoot with a view camera, but not impossible. Getting to the top of the canyon is rewarding for shooting, but very difficult if you're carrying an 8 x 10 in a backpack along with a tripod. The guide books say to stay on the right side of the canyon to get to the top (the way I went up), and it is possible, but a lot steeper climb up. It's also harder to climb down than it was to go up, so be prepared for a very strenous hike if you're going to the top.
Here's a shot I took up at the top (cyanotype over platinum).