Everything will depend on the process followed. If you applied outside the United States, you must register for an interview. The waiting time for an appointment is between 20-30 days. The process of issuing the visa, from the day of the interview until the passport is ready to withdraw, can take 5-10 business days.
If you apply while in the United States, the documentation will be reviewed by the California Migration Service Center. This procedure is carried out entirely through the exchange of documentation by mail; The applicant does not need to appear to an interview. The Migration Service Center can take about 3 months to review the case and approve it. Applicants have the option of paying for an expedited review process.