He was transferred to an undisclosed rehabilitation facility.
Stow suffered serious brain injuries from a March attack in the stadium parking lot after the Los Angeles Dodgers' home opener.
"When Bryan came here, he was in a comatose state, and when he left us today, he was able to begin to speak, interact with his family, and he's now beginning to eat as well. And he's making dramatic progress," said Dr. Geoff Manley, SFGH Chief of Neurosurgery, who led Stow's care team.
According to San Francisco General Hospital, Stow arrived at SFGH from LAC+USC Medical Center on May 16 after being severely injured in an assault on March 31 in Los Angeles, where he suffered traumatic brain injury. He underwent a decompressive craniectomy in Los Angeles, a life-saving surgical procedure to remove a piece of the skull to relieve pressure caused by brain swelling resulting from the beating.
That procedure allowed him to live, according to SFGH, but the extent of his recovery remained unknown. Manley replaced the missing skull fragment on August 10 with a custom prosthetic bone flap. Shortly afterward, a shunt was placed to drain fluid from Stow's brain to protect him from further harm.
"Bryan has been an extremely challenging patient," said Manley. "It has been a roller coaster, but he is young and strong and has made tremendous advances. To get this far, it was vital that he be at a place that specializes in acute care for brain-injured patients. Now it is equally important that he receive care from a place that specializes in rehabilitation for patients with brain injuries."
Two men have been charged in the beating in Los Angeles.
The Associated Press contributed to this report.