If you plead guilty the court will give you some time to remand yourself to jail. Fortunately the LA jails are over crowded - so you probably will spend very little time in custody .
Assuming that the assigned court date you're referring to is the initial arraignment and that you were released with a citation and promise to appear following your arrest, it is highly unusual to be taken into custody on that date.
In fact, unless charged with a felony DUI or ordered by the court to attend, a defendant may retain an attorney to make the appearance at arraignment in his place.
In the event of a guilty or no contest plea to the DUI, the court will typically set a turn-in date for jail (or alternative work project, if the defendant qualifies).
In some cases that are especially egregious or if there have been a series of failures to appear, it is possible to be immediately taken into custody. In the circumstances you've described, if you are faced with jail time, you will be given time to report for that sentence. I'd definitely recommend talking to an attorney. Good luck.
Your question is a little ambiguous. Usually when people are talking about showing up on their ticket, it often means thats their first appearance. If that is the case, no, you enter a plea the first day you show up and the case continues. If you plead guilty or will be pleading guilty you will most always be given time to surrender.
It is unlikely the Judge would take you into custody on the first court date. Most cases take time to plea bargain. Also, judges in the Santa Clarita area are pretty fair and give people time to surrender to get their affairs in order. In respect to a 2nd DUI, if the alcohol blood level is low, you may be able to strike your 1st DUI and end up with classes and a fine. Further, a lot of people are under the misconception that you must serve mandatory jail time on a 2nd DUI conviction. This is not true. There is actually a penal code statute which allows for 10 days community service in lieu of jail.
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