"Fans were lined up at a block long barricade screaming for him," an onlooker tells Us Weekly of the single star. "A couple different groups were singing 'Happy Birthday' to him."
Cooper happily posed for pictures with fans before catching up with Silver Linings Playbook director David O. Russell. Later that evening, the filmmaker, 54, presented Cooper with the Desert Palm achievement award.
"Hearing his speech was the ultimate birthday present, I have to say," Cooper told USA Today backstage. "It just reminded me of the trust he put in me to tell the story. And how deeply personal it was for him."
Despite his recent breakup, the honoree seemed to be in high spirits while mingling with Naomi Watts and other high-profile stars. Cooper and Saldana, who met as costars in The Words, initially split in March 2012 following a three-month courtship; they quietly rekindled their romance later that fall.
Prior to his relationship with the Avatar actress, Cooper romanced Renee Zellweger for two years and briefly dated Olivia Wilde and Jennifer Lopez. He was also married to actress Jennifer Esposito for four months from 2006 to 2007.