I went through Lower Antelope last year...there is only the one group running the show, and as long as you have decent looking equipment, you can opt for the self-guided 2 hour "tour". I would strongly recommend mentally preparing yourself to bracket your exposures, some scenes are probably the equivalent of 25+ stops of dynamic range, such as this one:
sand and time by posthumus_cake ([url=http://www.pinnaclephotography.net]www.pinnaclephotography.net)[/url], on Flickr
For me, the 2 hours were not enough, I could have easily spent twice that duration, and Lower Antelope is only a few hundred feet long. Keep looking for compositions with multiple layers to maximize the shift in light intensity/tone...
eye of the dragon by posthumus_cake ([url=http://www.pinnaclephotography.net]www.pinnaclephotography.net)[/url], on Flickr
And if you are in the Page area, you might as well shoot Horseshoe Bend while you are at it...
Horseshoe under the stars by posthumus_cake ([url=http://www.pinnaclephotography.net]www.pinnaclephotography.net)[/url], on Flickr
Beautiful shots! Are those the true colors that one sees or are they altered in PP?
The color hues are...fairly accurate (I shot with a slightly cooler color balance) but the saturation was boosted a bit in post. The color balance to the eye was a bit more orange, a bit less purple, though that would change if a cloud moved in front of the sun. The color shift is quite visible to the eye and since it is a slot canyon, the angle of the sun is the critical effect for what colors you will be getting...for example, when the sun is directly overhead in June or only indirect in December, you will be seeing quite significant differences in color intensity and hue spectrum. The primary factors here are the angle of the light and intensity. Each time the light bounces off a wall, it looses intensity and looks cooler to the eye. Since the canyon walls are so organically irregular, one spot might contain darker areas where light had to bounce off 3-4 walls to get there and another brighter spot with only 1-2 bounces, that would appear much, much warmer in hue.
As a side note, this color phenomena also applies to the Narrows in Zion...or would if the Obama administration hadn't thrown a temper tantrum and closed the National Parks...which is a real pity...hopefully that situation will be resolved by late October/early November (best times for Zion).