Wow, you guys are all having that much trouble with Cazadores? This is what I usually do:
1. Go into sneak mode
2. Pull out Incinerator
3. Wait for them to cluster close together
4. PHOOMPH PHOOMPH PHOOMPH PHOOMPH
5. Profit.
Combined with Boone, I had no problem taking out entire swarms at a time at level 10. Deathclaws, on the other hand, are still able to kick my ass if I don't snipe them from the other side of the map, and I'm at level 24 right now.
Honorary award goes to Giant Radscorpions, due to how they're everywhere the developers don't want you to go early on, can spot you from incredibly far away, and WILL. NOT. STOP. CHASING YOU. EVER. And they laugh at your Cowboy Repeater/Plasma Rifle/Hunting Rifle/whatever your current most powerful weapon is before about level 20.