The DMV proceedings and the criminal case are mostly separate. Under these circumstances, you are probably stuck with the DMV suspension.
The DMV suspension is probably based on the "zero tolerance" rule that a person cannot drive with a blood alcohol level of .01 percent or greater.
If you actually went to trial and were acquitted of Vehicle Code §23136(a), an infraction of driving with BAC over .01 when you were under 21, you would be entitled to have the DMV suspension overturned. (This requires an actual "not guilty" verdict; a dismissal is not enought.)
If the District Attorney had actually received and reviewed the police reports, and decided not to file charges of Vehicle Code §23136(a), you could ask the DA to file a form DS-702 with DMV, explaining why the charges were rejected. This would give you a right to a renewed DMV hearing. (Did you request a DMV hearing within ten days of your citation, or did you miss the deadline, making the suspension automatic?)
DMV hearings are very technical in nature, and are extremely difficult to do on your own. Even if you got a new hearing, it would be difficult to win without an attorney's help.
