A group is launching an effort to save a downtown Portland plaza and almost three dozen other city spaces from being sold and developed. The Portland Press Herald reported that the Friends of Congress Square Park filed an affidavit for a citizen’s initiative on Friday. It would add Congress Square Plaza and several other city properties to Portland’s land bank. The group is trying to change the city’s land bank ordinance to require eight City Council votes or six votes and a citywide referendum to sell a property in the city’s land bank. The council is scheduled to vote on Monday on whether to sell two-thirds of the plaza to Rockbridge Capital for $524,000.