I took deathclaw promontory at lvl 11

mostly using a heavy incinerator (after butchering everyone at Hoover Dam), also planting all the explosives I had around the place.
Worst thing was by the end I had very low ammo, less than a clip for my incinerator and minimal MF/energy cells. Save, come back and oh fantastic, I'm being chased by an army of deathclaws.
Turns out you can't swim to Caesar's Legion though, who knew huh? (Yeah it was my second playthrough, first never went there except at endgame)