Thank you again to everyone.

I use poles while hiking on trails with loose sand and gravel. They just help me move a little faster and more confidently. I agree that light hiking boots like Hi-Tec or the equivalent are a good idea. I made the mistake of taking a couple of short walks to overlooks. etc. in sandals, and regretted it because the sand really did get everywhere. Sandals would probably be fine in the Carlsbad Caverns as long as you didn't get stepped on by someone else.