The U.S. Senate may vote on the issue Tuesday.
Several dozen demonstrators were marching, carrying candles and chanting Monday evening outside the building in Chicago that houses the state Republican Party.
They were planning to spend on the night here in anticipation that the senate could vote on the law as soon as Tuesday.
Supporters gathered in the basement of a Melrose Park church. Several dozen supporters of immigration reform were organizing, rallying, and making phone calls to senators who they believe may be opposed to immigration reform.
"What I remember is... going to school, making friends, I learned the language, graduated from high school here," said student leader Rogelio Diaz. "I want to contribute to this country."
They hope to make 65,000 calls - the number of undocumented students they say graduate from high school every year with little opportunity for further education.
Undocumented student Ariano Selgado, 17, has been here since she was 6. She said if the DREAM Act passes, her dream of going to UIC for social work could come true.
"Not asking for anything for free - we're not taking anything from anybody," said Selgado. "We just want to give back to the country that we've always lived in."
Some immigration reform opponents believe the bill would be too costly, especially in this economy.
"American taxpayers have said no, no, no, before to the DREAM Act," said Illinois Minuteman Project Director Rosanna Pulido. "And now they don't say no; they say, 'hell no.'"
Earlier, supporters gathered at the federal building as two young undocumented teenagers tried to apply to enter the Navy, another provision in the DREAM Act. They were too late.
"They told us it was closed, but... offices like those will be always closed for us," said one of the teens, who is named Ernesto.
Similar rallies like the one in Chicago are going on in major cities around the country, and on Tuesday a group of business leaders is also planning a news conference. They want to urge Republican leaders not to stand in the way of the DREAM Act.
