Yes there advlts. I'm level 20 with 100 guns (95 plus Duster) and they're mere annoyances.
Well ive done two playthroughs (the first one never got completed i started over) and the first one was pretty far into the game, a good 17 hours maybe? and i never found a single cazador, no young ones, and no advlts. As well i've NEVER seen a deathclaw. I started my fallout career with FO:3, played through once (a lot of the side quests finished too) and never seen one, that includes what ive played on NV as well.