I am sorry but Maryland is no exception to the 2 party law. The courts have came out and said their is no expectation of privacy in a public place.
From the Maryland State Code
Md. Code Ann., Courts and Judicial Proceedings § 10-402: It is a felony to intercept a wire, oral or electronic communication unless all parties to the communication have consented. But all-party consent will not make the recording legal if there is a criminal or tortious purpose behind it.
Disclosing the contents of intercepted communications with reason to know they were obtained unlawfully is a crime as well.
Violations of the law are felonies punishable by imprisonment for not more than five years and a fine of not more than $10,000. Civil liability for violations can include the greater of actual damages, $100 a day for each day of violation or $1,000, along with punitive damages, attorney fees and litigation costs. To recover civil damages, however, a plaintiff must prove that the defendant knew it was illegal to tape the communication without consent from all participants. Md. Code Ann., Courts and Judicial Proceedings § 10-410.
State courts have interpreted the laws to protect communications only when the parties have a reasonable expectation of privacy, and thus, where a person in a private apartment was speaking so loudly that residents of an adjoining apartment could hear without any sound enhancing device, recording without the speakers consent did not violate the wiretapping law. Malpas v. Maryland, 695 A.2d 588 (Md. Ct. Spec. App. 1997); see also Benford v. American Broadcasting Co., 649 F. Supp. 9 (D. Md. 1986) (salesmans presentation in strangers home not assumed to carry expectation of privacy).
It is a misdemeanor to use a hidden camera in a bathroom or dressing room. It is also a misdemeanor to use a hidden camera on private property "for purposes of conducting deliberate, surreptitious observation of a person inside the private residence," or in a private place with "prurient intent." Md. Crim. Law §§ 3-901, -902, -903. A person who is viewed in violation of these statutes has a civil cause of action.
http://www.callrecordingcenter.com/maryland-call-recording-law.php
In-person Conversations
Before recording an in-person conversation, you must determine whether it is considered a private conversation.
If a conversation can be overheard naturally in public, without the aid of electronic devices, then the conversation is not considered private and can be recorded. For example, if you are at a park and hear two people arguing loudly in front of you, this is not considered private.
Read more :
http://www.ehow.com/list_7298914_audio-surveillance-laws-maryland.html
http://www.ehow.com/list_7298914_audio-surveillance-laws-maryland.html