My question involves criminal law for the state of: California in SF

I received an infraction: MPC 21

first, i have been unable to find that code online and what it states.

secondly, what would be the best plea to get my fine lowered and possible ask the judge to dismiss the infraction in exchange for community service? is this even possible?

i know that you can't expunge infractions, so what i'm trying to figure out is how can you dismiss infractions off your record? how long do they stay on your record?

Thanks!