The signs, which have an extra E in the word street, have been up for nearly a week with the blunder.
A man with a sharp eye finally noticed it and posted it to Facebook. His friend then posted a photo of one of the signs on Instagram.
Officials said the signs probably went through six pairs of eyes before being produced with the spelling error.
"I couldn't believe it. It's an easy word to spell," said Jay Nunez, a San Pedro resident. "Maybe somebody wanted to say streeet."
Fellow resident Roque Marquez wondered if the extra letter was intentional.
"Maybe they just thought it would be something kind of cool - go with the three Es and go with that," he pondered. "But I guess they're going to change it up and correct it."
Crews were scheduled to start taking down the signs to get them fixed on Thursday.
City leaders aren't necessarily passing the buck, but they say they had nothing to do with creating the signs, which were done by a design firm selected by a committee overseeing local improvements.
The Associated Press contributed to this report.