This is a well known one and is one of the ways the observatory people promote their location. Even before I was even into location hunting, as a kid, I could have told you where this one was.
There are some differences with the way it is now compared to then, but it is obvious that it is the same area. When you are facing the front of the observatory just follow it around on your left and you will run into this place.
Personally, I would have kept the lug wrench and not thrown it like James did. Ehh, I would not fight fair in a situation like this. That is just me though.
As I mentioned, part of the way they promote this place is with this movie. There is a plaque located here dedicated to James Dean. You can see the Hollywood Sign in the background. If you want to go to the observatory it is free. There are some short science movies they show for a fee, but the rest is free.