We are not attorneys and do not offer legal advice. If you are facing criminal charges we suggest you talk to a professional attorney.
By the time you are sentenced you will have either been found guilty in a trial or plead guilty to a crime. If you plead guilty you will most likely have negotiated your sentence first - remember, this is just an agreement between you and the prosecutor. The judge can reject the agreement if he feels like it but this is very uncommon with the volume of cases the Los Angeles County Jail sees on a daily basis. Your attorney can advise you in this situation.
Los Angeles County Jail inmates typically fall in two categories - inmates sentenced to one year or less and inmates waiting to be transferred to state prison. If you are being sentenced to actually serve time in Los Angeles County Jail most likely the sentence will not be for longer than a year - if you are charged with multiple counts then the sentences will most likely run concurrently, meaning you serve them all at the same time. It is possible, however, that you will be sentenced to more than a year though it is uncommon.
Most inmates don't serve anywhere near the full term of their sentence - if you don't have violence on your record you will most likely serve 10-25% of the time you are sentenced to (depending on the current jail population). If you have violence supposedly you will serve 50% or though, but there are notable exceptions to this rule. One of our interviewees was sentenced to a year for Assault with a Deadly Weapon and served just 37 days before being sent free.
When you are negotiating with the prosecutor (through your attorney) remember to be patient if you aren't given a good offer - the longer you wait to take an offer the more likely the prosecutor will cut time off your sentence in order to avoid a costly trial. Some people do prefer to get the sentencing process out of the way, however, and start serving their time - in Los Angeles you may be OK doing this considering that you will only serve 10% or so for a first-time stay but always consult with your attorney on what is the best strategy with your case.