Elvira Arellano, the illegal Mexican immigrant who has avoided deportation for a year by taking refuge inside a Humboldt Park church, said today she plans to leave her sanctuary to participate in a new push for immigration reform in Washington. At a news conference at the West Side church where she has been living for exactly a year, Arellano said she intends to use her status as a figurehead for the nation's estimated 12 million illegal immigrants to leverage support for more lenient legislative reforms. . . . It was not immediately clear when she would leave the church. She...