Police said Gallo was speeding when he ran a red light, slamming into car and killing rookie pitcher Nick Adenhart, 20-year-old Courtney Stewart and 25-year-old Henry Pearson, in Fullerton on April 9. Adenhart, 22, had pitched six scoreless innings for the Angels hours earlier.
A fourth person in the car, 24-year-old Jon Wilhite, was critically injured in the accident. Wilhite is a former catcher for Cal State Fullerton's baseball team.
Wilhite attended Monday's arraignment, but is reportedly still recovering the injuries.
Gallo was on probation for a prior drunk-driving conviction, and authorities said his blood-alcohol level on the night of the fatal accident was nearly three times the legal limit.
Gallo's attorney, Randall Longwith, said he will seek a change of venue for his client.
"I just think the emotion here, it is so heated here, specifically in Orange County, Fullerton even more so," he said. "I don't think in any way we can get a fair trial here."
Deputy District Attorney Susan Price said she has not seen such a request.
"If we get one, we're prepared to respond to it. It certainly won't be the first change of venue motion that we've received here in Orange County, and we're prepared to deal with it if necessary," she said.
Gallo, who is being held on $2 million bail, will be back in court on July 31 for a hearing to set a trial date.