Many soccer fans in Queens say they favor a stadium, but they do not want to lose access to the public fields that they use. Alfonso Vargas, the president of Allfut, a soccer alliance that comprises 14 leagues, 400 teams and about 5,000 players who compete at the park, said he supported the proposal as long as the local soccer leagues would be accommodated. [...] Parks groups seemed more alarmed. Though the park is listed as having nearly 900 acres, the actual amount of land devoted to public recreation there is far smaller, when land used by the U.S.T.A., the Mets, the M.T.A. and the Queens Museum is subtracted.