For an "expungement" (technically, a dismissal under Penal Code section 1203.4), you must have completed your probation or have it terminated early. Expunged convictions must be disclosed to the nursing board when you go for a license, so it's not the complete cure to be able to hide it. If an expungement is granted, you can tell private employers that you do not have a conviction.
Since your case is still pending, and given your future goals, I would strongly encourage you to consult with a local criminal defense attorney that routinely practices in the court where your case will be heard. They can best advise you how to proceed and what you can do for the best possible outcome. They may be able to convince the DA to offer you a diversion program that ends up with a dismissal instead of a conviction that has to be expunged.
Every case is unique, but this one is worth discussing face to face with a defense attorney.
For those people trying to recover from a criminal conviction, an expungement is often an essential step towards rebuilding their lives. An expungement results in the dismissal of the earlier criminal case. It allows a person to answer on job applications that he does not have a criminal conviction. However, the record of the expunged conviction will be discovered if that person applies for a government job or a job which requires a government-issued license, certificate or permit, or a job which involves a security clearance.
Unfortunately, an expungement alone does not prevent the expunged conviction from being considered and used to refuse or revoke government licenses and permits, such as a real estate sales license, teaching credential, bus drivers license, security guard certificate, et cetera. However, an expungement will reduce the weight given the expunged conviction by the licensing agency.
An expungement does not remove an expunged conviction from a person’s "rap sheet." California and FBI criminal history records will still show the conviction and a dismissal "per Penal Code section 1203.4." An expungement does not seal or otherwise remove court case files from public inspection. Anyone who knows where to look will be able to find the court case file.
An expungement does not prevent the expunged conviction from being used as a "prior" to increase punishment in case of a subsequent conviction for the same or similar offense. It also does not prevent the expunged conviction from being used for impeachment purposes if called as a witness.
Although an expungement is not a panacea, it does demonstrate a person’s rehabilitation in the eyes of the court. It is definitely worth doing. Depending on a person’s prior conviction and situation, they may or may not be eligible for an expungement. A good defense attorney can advise you on the best way to pursue an expungement.