It sounds as if you were cited by a ranger in the Glamis Sand Dunes in Imperial Valley which is a California State Park. Since it is a state park it would appear that you were cited under California laws for driving your dirt bike with a suspended license.

California has its own site for Off-Roadway Motor Vehicle Recreation and here it notes that a driver’s license is not necessary to operate an OHV in most areas. However, if your driving privilege is suspended in California, you may not operate an OHV on California public lands.

This CA Off Roadway website even notes that the law in which states you cannot drive with a suspended license is California Vehicle Code (CVC) 14601.1(e).

CVC 14601.1 states that no person shall drive a motor vehicle when his or her
driving privilege is suspended or revoked if the person so driving has knowledge of the suspension or revocation. It goes on to say that any person convicted under this section shall be punished as follows:

• Upon a first conviction, by imprisonment in the county jail for not more than six months or by a fine of not less than three hundred dollars ($300) or more than one thousand dollars ($1,000), or by both that fine and imprisonment.
• If the offense occurred within five years of a prior offense which resulted in a conviction of a violation of this section or Section 14601, 14601.2, or 14601.5, by imprisonment in the county jail for not less than five days or more than one year and by a fine of not less than five hundred dollars ($500) or more than two thousand dollars ($2,000).

Subsection (e) states specifically that this section also applies to the operation of an off-highway motor vehicle on those lands to which the Chappie-Z'berg Off-Highway
Motor Vehicle Law of 1971 (Division 16.5 (commencing with Section 38000)) applies as to off-highway motor vehicles, as described in Section 38001.

So it would appear from these California laws that if this is your first conviction then you will be facing a fine of between $300 and $1000 or county jail time of not more than 6 months or both. The court listed on your citation should be able to give you more information on your specific situation since your suspension was due to a DUI. The CA DMV may also be able to advise you on the penalties you could be handed due to driving your dirt bike with a suspended license.