It shall be unlawful for any person, individually or as a member of any group of persons, to loiter, stand, sit, lay or remain upon or within any street, sidewalk, crosswalk, alley or parking lot generally open to the public or other public way or otherwise occupy any portion thereof with the intent or purpose to block, obstruct or interfere with the free passage of any pedestrians thereon or the orderly free flow of vehicle traffic on the street or public way.