It depends on what agency or record company. Some just looking through what I have sent and other people have sent to that address and gotten things back, these people do respond:

Avril Lavigne-RCA Records
Amber Tamblyn
Michelle Trachtenberg-United Talent Agency
Beyonce- Creative Artists Agency

But, I do not think the street its on matters, but the agency might.

Were the letters going to an agency on Wilshire Blvd?

I think ICM has an address there, and although it wasn't a success as such, I got a RTS back from them, which at least means it got to the right place.

Does anybody ever have a success from there? I have sent out over a hundred letters to that addy and never recieve anything. Just curious