By JOHN QUINONES (@JohnQABC) , BEN NEWMAN and ROXANNA SHERWOOD April 25, 2012 About a half-million people call an estimated 2,000 poor and isolated "colonias" home. The sparse communities dot the landscape of south Texas, along the more-than-1,000 miles the state's border shares with Mexico. A staggering 100,000 of the residents -- mostly all U.S. citizens -- are children. Watch the full story on "Nightline" tonight at 11:35 p.m. ET/PT. Maria Castro, 12, is among them and lives in a small house that her father built with her mother, nine of her sisters and brothers, and two cousins. Outwardly, Maria seems like most other American girls her age. She wants to look her best at school, rides a yellow school bus to get there, and enjoys playing flute in the school band. "My dream is to be someone in life. That's all," she said. "I actually want a better life than we have right now." At school, Maria finds refuge from her life back at home in las colonias, marked … [Read more...]