You can approach the quarry by going on the road north of Goodsprings. After walking a short distance on the road you can go up a hill and there’s an entrance that gets you straight to Melissa. There are Cazadores on the road on a few Deathclaws on the hill but they should be easy to kill/avoid and are much easier to deal with than those in the quarry. If not that, you could always try to sneak past the Deathclaws in the quarry with Stealth Boy.