The ordinance is in the city's Municipal Code, under Title 4 (Public Welfare, Morals and Conduct), Chapter 6 (Nuisances), Article 2.
Under "Prohibited Noises Enumerated," and Maintenance Equipment it states:
"The use and operation of any noise-creating commercial or residential landscaping or home maintenance equipment or tools including, but not limited to, hammers, blowers, trimmers, mowers, chainsaws, power fans or any engine, the operation of which causes noise due to the explosion of operating gases or fluids, other than between the hours of 8:00 a.m. and 7:00 p.m. on weekdays and 9:00 a.m. and 7:00 p.m. on weekends and holidays. (§1, Ord. 1753, eff. November 8, 1990)."
In plain English, you can only operate leaf blowers between 8 a.m. and 7 p.m. on weekdays and between 9 a.m. and 7 p.m. on weekends and holidays.
But as you can see, the ordinance went into effect back in 1990. So, maybe it's time for the city to revisit that issue?