Young Dancemakers Company will present an ensemble of 17 talented high school dancer/choreographers who will choreograph and perform their own works in 7 free performances in Manhattan, the Bronx, Brooklyn and Queens.   The teens create their works under the direction of founder Alice Teirstein and music director William Catanzaro, and will also appear in an excerpt from a Paul Taylor work, set by Richard Chen See, former Taylor principal dancer.   All performancs end with a "Dance With Us" improvisation with the audience invited up onto the stage.   Please visit the website www.youngdancemakerscompany.org  for locations of performances.