Encounter any problems with this walkthrough? Have comments? Let us know!
You can learn about the raiders from both Wallace at the custom's office in Vault City and Stark within the inner city. Either way, it's an unknown green area about four grids due north of Broken Hills and in between Vault City and Broken Hills. When you first enter the map, it's most likely you'll enter at the cave camp entrance.
Enter into the cave, and beware of the many traps and holes (which you can spot with a high Perception) scattered along the ground in this large area. If you fall down any of the holes, you'll end up in a giant radscorpion nest, which you can pick up a few items off the ground. The regular way into the scorpion nest is the ladder on the northern end of the cave area. To the east is the entrance to the Raider's barracks area, where all of them reside and are waiting for their chance to kill you.
Take the entrance when you're ready and you'll be confronted by a couple traps and locked fence doors. The Raiders inside can pick you off from a distance with their long-range weapons, so either have one of your own and pick them off first, or something that can kill them quickly.
Search the northern part of the barracks for three armor-wearing leaders, each of them guarding a footlocker containing their dogtags and some round rubbery items. These are the toughest Raiders, so beware. When you've opened the footlockers, taken all three dog tags, and examined them, you'll know the combination to the safe in the northeast room. Disarm its trap, open it using the combination and take the account book and whatever else you find.
When you've dealt with all the Raiders, leaving the tribal guide alone (if you're feeling good), you'll receive a message that you've weakened their strength and can now go back to Vault City and speak with first citizen Lynette for a couple rewards (if you bring the account book). Tell her that you've defeated the raiders and then show her the book.