Pittsburgh's G-20 story: Take an expressway from town and disappear into desolate 'hoods and encounter the civilization of menace. Pittsburgh, a dual city! The glass wonder of PPG Place and/or the G-20 Summit is a faded memory. Here in the 'hood lives lie abandoned as far as the eye can see.   http://www.youtube.com/watch?v=IEukcWW5dM0   That is: For the most part, African-American Pittsburgh seems to be invisible, not only to the public relations hucksters who tout Pittsburgh's successes, but we are equally invisible to the protesters.    Certainly, black Pittsburgh is as proud as anybody is that the black President we worked so hard to elect has selected Pittsburgh as the host of the G-20 Summit. We even enjoy the re-invention of Pittsburgh from a dirty, smoky steel-churning history to the bright, clean, green financial success that the business leaders and politicians boast about so loudly. Nobody is more proud of the Super Bowl winning African-American coach of the Pittsburgh Steelers, Mike Tomlin. But none of that feel-good stuff erases the pain of the stubbornly high unemployment among African American young adults and the staggering dropout rate for young black males from the public school system.