The crash was reported shortly after 2:30 p.m. at Magnolia Avenue. The bus company, Sina Coach, said there were 22 passengers and the driver on board.
According to the California Highway Patrol, all passengers suffered minor to moderate injuries. Many of them had to crawl out of the emergency hatch on top of the bus.
The driver, 35-year-old Jian Fei Duan of Baldwin Park, sustained minor injuries and was not transported to the hospital.
The driver was traveling 65 mph when he lost control and hit the center median guardrail. The CHP said that is "unsafe speed for roadway conditions."
It was raining at the time of the crash, but it's unknown if the wet weather caused the accident.
The bus was heading to Garden Grove from the Pala Casino Spa & Resort in San Diego County.
Around the same, another tour bus crashed on the southbound 15 Freeway near Fallbrook in San Diego County. At least one person was killed in that crash.