Treasury Secretary Timothy Geithner acknowledged that it is still a "tough economy" for most Americans, and warned it's possible the unemployment rate will go up for a couple of months before it comes down as more people enter the labor force. When they see a little hope that there may be jobs out there, they start to come back in again. And that can cause the measured unemployment rate to go up — temporarily," Geithner told "Good Morning America's" George Stephanopoulos in an exclusive interview. "But what we expect to see, and I think most forecasters expect this…is an economy...