The flag of San Pedro de Macorís can be seen in a photograph online here (image). The flag features the municipal coat of arms centered on a white field. There may be some inscription above the coat of arms, but I am unable to tell for sure from the photographs I found. Randy Young, 23 January 2016
San Pedro the Macorís is the capital city of the province of San Pedro de Macorís in the southeastern part of the Dominican Republic. Founded in the late 1800s by Cuban expatriates, the city has been the home to many firsts in Dominican Republic history, including the first sugar mill, the first firefighting corps, and the first town to have a telephone center. The city is home to Eastern Central University (Universidad Central del Este, UCE).
Source: Wikipedia article Randy Young, 23 January 2016