In 1918, brothers Jerónimo, Rosa, Gerardo and Jaime Fonalledas acquired  of land previously known as "Las Monjas". This land was property of Don Pablo Ubarri Capetillo, the Count of Santurce. By 1920, little by little cane harvesting was eliminated with the intention of using the land for the creation of a milk company, eventually known as "Vaquería Tres Monjitas". In 1950, the metropolitan area of San Juan was growing rapidly. The planning board began to build the project and ordered the development of the lands. It is then that the Fonalledas brothers came up with the idea of establishing a regional shopping center in the "Las Monjas" property. The planning board included a space of 15 acres of land for a shopping center in its development plan. In 1962, the plans for the construction of a shopping center and the negotiations with tenants began. In April 1967, construction of Plaza Las Americas began under the direction of engineer Peter Jacobson. On September 3, 1968, Plaza Las Americas held its grand opening. It was the first enclosed shopping center in Puerto Rico and the largest in Latin America at the time. The project was inaugurated with a total of 79 establishments, a twin cinema and parking for 4,000 vehicles. One hundred percent of the space is rented and nearly 2,000 people were employed in the new mall. The primary anchor store is a three-level (261,500 square foot) J. C. Penney. It was the chains first location outside the fifty states and its largest operation between 1968 and 1971. The mall also housed two San Juan-based department stores as its second and third anchors. These are a two-level (76,500 square foot) Gonzales Padin and (22,000 square foot) Velasco. Inline stores include Martha Washington Ice Cream, Zale Corporation, Florsheim Shoes, La Esquina Famosa (mens clothing), Bakers (shoes), Zale Corporation, Clubman, Marianne Shops, Singer Corporation Sewing Center, New York & Company, Thom McAn, La Favorita and First Federal Savings Bank, along with an F. W. Woolworth Company, Farmacias Gonzalez (pharmacy), La Cosa (curios), La Tienda Sin Nombre (shoes), Bennys Toys, Pueblo Supermarket, travel agency and a full-sized hardware store. A small section had a second floor where medical and business offices were accessible. The following year, the architectural design of Plaza las Americas won the URBE Award for Best Commercial Architecture
Question: How many months after construction began on Plaza Las Americas did it hold it's grand opening?
Answer: 17