Sometimes it can take a while, especially if you are out of custody - the priority is for serious cases (like vehicular manslaughter), followed by in custody cases, then out of custody. They will send it to the DA's office, who will then decide whether or not to file based on the totality of the circumstances. If you were cited out (or booked and released), make sure you appear on the date of your citation. Otherwise, you have to wait for a notice to appear to be sent to you. Good luck.
You will be waiting by the mailbox a long time if you expect them to send you anything. When you were arrested you may have received a vial number and the local crime labs website to look up the results yourself. They take about two weeks to obtain. You have the court date from the police officer. Make sure you attend that date or hire an attorney to do so. The best way to get a copy of the discovery in your case prior to the court case is through the DMV as long as you scheduled a hearing within 10 days of the arrest.
Your blood results will not be mailed to you. The D.A.'s office in the Vista Courthouse will provide the results to your attorney, who can then provide a copy to you. If you haven't already, you're going to want to consult a defense attorney about what can be done on your behalf. If you have any questions in that regard, please feel free to call my office to arrange a free consultation.