The crash happened at approximately 2 a.m. in the middle of the popular restaurant and nightclub area, close to the city's convention center.
Officials said that about 25 people were injured as they were spilling out of a nightclub at closing time.
Police said the driver, 42, told them he blacked out prior to the accident. Officials confirmed that alcohol was not involved. The cab was traveling slowly, around 15 mph, and the crash did not appear to be intentional, authorities said.
Officials said 23 people were hospitalized, four with critical injuries. One woman, 42, reportedly was pinned against a wall by the cab and had her leg severed. None of the injuries was life-threatening.
"We're trying to determine what exactly caused the accident," said San Diego Police Lt. Rick O'Hanlon. "There's been some reports that he passed out. The detectives are interviewing him and are going to follow up on that and backtrack his whereabouts prior to the accident."
Security guards had to come to the rescue of the driver after angry bystanders attacked his cab.
The driver suffered a broken nose.
"When the taxicab went into the building, there were some people that were obviously upset, probably intoxicated, and they took it out on the taxicab driver," said San Diego Police Sgt. Art Doherty.
"He did sustain a broken nose, but we're still trying to determine if the broken nose was from the impact or from the disturbance after the impact," said O'Hanlon.
The driver, whose name was not released, was not arrested.
The Associated Press contributed to this report.