You might have noticed a series of posters going up around the city of a bearded dude in a black hat, with the caption “Do you know this man? If you do, you’ll be here . . . If you don’t, you should.” The figure in question is the one and only Panama-born renaissance man Rubén Blades, a Grammy-winning salsa singer who has headlined Carnegie Hall, a Harvard-educated lawyer, a human rights activist, an award-winning film and television actor (Crossover Dreams, Crazy from the Heart, The Milagro Beanfield War), the star of Paul Simon’s Broadway musical The Capeman, and a politician who lost a bid to become president of Panama but served five years as his nation’s minister of tourism. Blades, who has released such seminal albums as Escenas, Buscando América, and Tiempos and such memorable songs as “Pedro Navaja,” “El Cantate,” “Ojos del Perro Azul,” “Todos Vuelven,” and the always stirring “Muevete,” will be playing a free show on August 7 at the Damrosch Park Bandshell as part of the annual Lincoln Center Out of Doors festival. If you don’t know Rubén Blades, it’s about time you did, and this free concert should be just the right introduction.