Hello, everyone. This is a really late post but last year on May 17th, 2012 i sent a letter to Dule Hill (from USA's Psych), and after about a year later i got the letter back with the photo signed, on July 18th 2013.
I used this address:
Dule Hill
ICM Partners
10250 Constellation Blvd
9th Floor
Los Angeles, CA 90067-6209
USA