If you're represented by private counsel, you should ask that attorney to seek a continuance with the DMV. You should beware, though, that even "beating" the charge in court does not guarantee you that the DMV hearing officer will reach the same result.
You have an absolute right to be represented by an attorney at your DMV hearing. If you have not secured an attorney on the date and time your hearing is scheduled for, you can request a brief continuance to secure counsel. This are generally granted by the hearing officer assigned to your matter.