In terms of a preliminary exam, read this. I would not expect a preliminary exam for a charge this minor.

If you mean a pretrial, there should be a prosecutor present with whom you (or your lawyer, if you are represented) can discuss the charge and possible plea bargains.
Quote Quoting § 19-301. Possession of alcoholic beverage in open container in certain places.
(a) Definition; applicability.-
(1) This definition applies only in the following jurisdictions:
(i) Caroline County;

(ii) Carroll County;

(iii) Dorchester County;

(iv) Harford County;

(v) Montgomery County;

(vi) Prince George's County; and

(vii) Wicomico County.

(2) In this section, "unless authorized" means the possession and presentation of a written consent by the owner of the property.
(b) Prohibited activities.- A person may not possess in an open container any alcoholic beverage, as defined in this article, while:
(1) On the mall, adjacent parking area, or other outside area of any combination of privately owned retail establishments, commonly known as a shopping center, to which the general public is invited for business purposes, unless authorized by the owner of the establishment;

(2) On an adjacent parking area or other outside area of any other retail establishment, unless authorized by the owner of the establishment; or

(3) In any parked vehicle located on any of the places enumerated in this section, unless authorized.
As I read that statute, the definition provided in subsection (a)(2) only applies in the enumerated counties; the rest of the statute would apply statewide.