Make no mistake, the canyon is still beautiful and well worth seeing.
When I last photographed Lower Antelope nine years ago, I arrived early, was second in line behind a fellow photographer from France, and we were taken by ATV to the canyon entrance. We had the canyon to ourselves for the first 30 minutes and with full use of tripods. I have two friends who remember descending into the canyon via rope ladders and spending hours virtually alone, unguided. Those days are gone forever.
The canyon tours now push hundreds of people of all ages through the canyon every day, usually in multiple guided groups of 12-16 and you get about one hour in the canyon. No tripods, no camera bags, no backpacks, no purses, just a camera or two and water bottles.
Do the Navajo deserve to make tons of money on the canyons? Absolutely! It is long overdue and I have no quarrel whatsoever. I want all the proceeds to benefit the tribal people. Just know that this will not be a contemplative stroll through sacred ground.
So, here are some suggestions to help you get the most out of your photographic efforts. I carried two cameras on straps, a 14-24mm and a 24-120mm. Managing two cameras is tricky through some of the narrower passages, and up and down the steel ladders. If you have one on a chest strap it could be easier. I shot at 800-2000 ISO (this was at about 11am), f8 - f11 to ensure depth of field, mostly autofocus and, of course, stabilization on. Because the dynamic range can be super wide with deep shadows to bright sunlight, I would recommend exposing to the left. Exposure compensation about 1/2 to 2/3rds under and check the histogram. In this situation, it is easier to pull out the shadows a bit than to rescue clipped highlights. These shadows can be a nice compositional element. Clipped highlights, not so much.
I found that the vast majority of my "keepers" were shot between 14-40mm, but one really excellent image was at 120mm. This was unexpected as I thought they would fall in the 35-85mm range. I am not normally a fan of "shooting loose", but it is really important to give yourself enough room to crop later as you won't have the time to frame up the image properly in many cases. You don't want to clip some critical edges accidentally.
The purpose of the guides is to give information about the formations, but more importantly to keep people moving through. Pausing for more than a few moments is discouraged, so here is the strategy I used. In my group was a family with 3 small children and they were toward the back of our group, so I stayed at the very back of the group. I knew the family would be taking kid pics and selfies at every turn. They paused frequently, so I could take several images unencumbered and the guides would be busy trying to move that family along while I remained an innocent bystander. It worked. Take the time to assess the situation.
It can be a bit chaotic, but if you plan for and accept the situation, you can concentrate on getting some wonderful images and enjoy what is still one of nature's true works of art.