At least 14 days before the land use board shall take action upon any proposed acquisition of land in any town or city, it shall, by letter addressed to the board of selectmen in such town, or to the board of mayor and aldermen in such city, advise it of the proposed acquisitions. At the request of the selectmen in such town or the board of mayor and aldermen in such city where the purchase of such land is contemplated, the land use board shall grant a public hearing in such town or city, or at some other convenient place. Provided, however, that no land shall be acquired under the provisions of this chapter until the acquisition of the same shall be approved by a majority of the voters present and voting at a regular or special town meeting in towns, or by a majority vote of the board of mayor and aldermen in cities.