The Border Security, Economic Opportunity, and Immigration Modernization Act of 2013 (BSEOIM) has a cut off date of 12/31/2011 and that means that either through a stamp in your passport or through other means if you crossed the border illegally, you should be able to prove that you were in the United States by this date. Since this is one of the most important requirements, if you do not satisfy it, you are out of luck to apply for adjustment to Registered Provision Immigrant (RPI) legal status.
The only good news is that despite the big noise that politicians are making about eVerify and other programs to make illegal employment difficult, the reality is that American employers are addicted to undocumented workers willing to work for lower wages. As soon as the eligible group of illegal immigrants legalize under the 2013 Obama Immigration Reform, they would start to demand better wages and benefits, and will leave if they don't get them. In addition, many unauthorized immigrants are currently working in low-end jobs because they are unable to work for big employers who demand valid documents. They too will quit these jobs and this will create a huge demand for illegal workers and those immigrants who are unable to legalize can take these jobs, maybe even at higher wages due to greater demand. Obviously, there is a risk that you will be caught and deported, but the risk will actually go down as enforcement will be cut back assuming that all illegals have been legalized.