Several of us travel the 605 daily. It's real and not a prank. Look at the middle of the billboard. It has the Angel of Independence pon it. That's a monument in Mexico City. They superimposed a monument from Mexico City over L.A..
And if my geography is correct, the 605 sign is just a few miles from where Deputy David March was murdered by a Mexican citizen.
What a kick in the teeth...
I saw the one at Sherman Way and Woodley (mid SF-Valley), southeast corner, above the 7-11, facing north. It's definitely authentic and it is EXACTLY as the one depicted above. If vandals got to the signs, they defaced them absolutely identically -- which is basically impossible. If you go looking for it, make sure you get WoodLEY, not WoodMAN or WoodLAKE, which are also SFV north-south streets.
John & Ken (640 KFI-AM, which is also a Clear Channel station), raised hell about this on the air the other day, and have attempted to get hold of the Clear Channel coworker behind this treasonous stunt.