Holy crap. I've been here in LA a little over 3 years without finding an authentic Philly cheesesteak, but that all changed the other day. In Burbank, CA there's a place called "Philly's Best" on Olive Avenue and their Philly steak sandwiches are dead on
. They even have the bread shipped to them from back East to make sure it's 100% authentic and they have a few framed t-shirts from Pat's, Geno's and Jim's steaks in Philadelphia as if to pay homage to their Philly cheesesteak mentors.
So if you're in LA and in need of a good cheesesteak, take it from a former Philadelphia resident and go check that place out pronto! (I recommend getting one "with wiz" btw)