when I am eligable for expungement?

Well below you will find the law.  You will most likely need the aid of a criminal defense attorney to help you through the process.

Try www.attorneypages.com and the California State Bar attorney search to check on the lawyer's discipline history. 

Here is some information:

1203.4.  (a) In any case in which a defendant has fulfilled the
conditions of probation for the entire period of probation, or has
been discharged prior to the termination of the period of probation,
or in any other case in which a court, in its discretion and the
interests of justice, determines that a defendant should be granted
the relief available under this section, the defendant shall, at any
time after the termination of the period of probation, if he or she
is not then serving a sentence for any offense, on probation for any
offense, or charged with the commission of any offense, be permitted
by the court to withdraw his or her plea of guilty or plea of nolo
contendere and enter a plea of not guilty; or, if he or she has been
convicted after a plea of not guilty, the court shall set aside the
verdict of guilty; and, in either case, the court shall thereupon
dismiss the accusations or information against the defendant and
except as noted below, he or she shall thereafter be released from
all penalties and disabilities resulting from the offense of which he
or she has been convicted, except as provided in Section 13555 of
the Vehicle Code. The probationer shall be informed, in his or her
probation papers, of this right and privilege and his or her right,
if any, to petition for a certificate of rehabilitation and pardon.
The probationer may make the application and change of plea in person
or by attorney, or by the probation officer authorized in writing.
However, in any subsequent prosecution of the defendant for any other
offense, the prior conviction may be pleaded and proved and shall
have the same effect as if probation had not been granted or the
accusation or information dismissed. The order shall state, and the
probationer shall be informed, that the order does not relieve him or
her of the obligation to disclose the conviction in response to any
direct question contained in any questionnaire or application for
public office, for licensure by any state or local agency, or for
contracting with the California State Lottery.
   Dismissal of an accusation or information pursuant to this section
does not permit a person to own, possess, or have in his or her
custody or control any firearm or prevent his or her conviction under
Section 12021.
   Dismissal of an accusation or information underlying a conviction
pursuant to this section does not permit a person prohibited from
holding public office as a result of that conviction to hold public
office.
   This subdivision shall apply to all applications for relief under
this section which are filed on or after November 23, 1970.
   (b) Subdivision (a) of this section does not apply to any
misdemeanor that is within the provisions of subdivision (b) of
Section 42001 of the Vehicle Code, to any violation of subdivision
(c) of Section 286, Section 288, subdivision (c) of Section 288a,
Section 288.5, or subdivision (j) of Section 289, any felony
conviction pursuant to subdivision (d) of Section 261.5, or to any
infraction.
   (c) (1) Except as provided in paragraph (2), subdivision (a) does
not apply to a person who receives a notice to appear or is otherwise
charged with a violation of an offense described in subdivisions (a)
to (e), inclusive, of Section 12810 of the Vehicle Code.
   (2) If a defendant who was convicted of a violation listed in
paragraph (1) petitions the court, the court in its discretion and in
the interests of justice, may order the relief provided pursuant to
subdivision (a) to that defendant.
   (d) A person who petitions for a change of plea or setting aside
of a verdict under this section may be required to reimburse the
court for the actual costs of services rendered, whether or not the
petition is granted and the records are sealed or expunged, at a rate
to be determined by the court not to exceed one hundred twenty
dollars ($120), and to reimburse the county for the actual costs of
services rendered, whether or not the petition is granted and the
records are sealed or expunged, at a rate to be determined by the
county board of supervisors not to exceed one hundred twenty dollars
($120), and to reimburse any city for the actual costs of services
rendered, whether or not the petition is granted and the records are
sealed or expunged, at a rate to be determined by the city council
not to exceed one hundred twenty dollars ($120). Ability to make this
reimbursement shall be determined by the court using the standards
set forth in paragraph (2) of subdivision (g) of Section 987.8 and
shall not be a prerequisite to a person's eligibility under this
section. The court may order reimbursement in any case in which the
petitioner appears to have the ability to pay, without undue
hardship, all or any portion of the costs for services established
pursuant to this subdivision.
   (e) Relief shall not be granted under this section unless the
prosecuting attorney has been given 15 days' notice of the petition
for relief. The probation officer shall notify the prosecuting
attorney when a petition is filed, pursuant to this section.
   It shall be presumed that the prosecuting attorney has received
notice if proof of service is filed with the court.
   (f) If, after receiving notice pursuant to subdivision (e), the
prosecuting attorney fails to appear and object to a petition for
dismissal, the prosecuting attorney may not move to set aside or
otherwise appeal the grant of that petition.
   (g) Notwithstanding the above provisions or any other provision of
law, the Governor shall have the right to pardon a person convicted
of a violation of subdivision (c) of Section 286, Section 288,
subdivision (c) of Section 288a, Section 288.5, or subdivision (j) of
Section 289, if there are extraordinary circumstances.