If you have your own equipment, go to the rock shop in Delta, and get permission (free)/sign a waiver to dig their pit - it's right next to the fee one. The lady in the shop is really nice, and she can give you directions to get permission/sign a waiver for the Dugway geode pit. We checked out the free BLM area nearby the other trilobite spot, but didn't find any trilobites there. Take newspaper, paper towels to pad your finds.
Good luck - Utah is FULL of great rocks & fantastic scenery!!! We enjoyed an extended visit there recently and had a blast.