Crab Grass - Too Late?

Is it too late to lay down a pre-emergent?  I've been so tied up with work 
and other stuff that I haven't had a chance up to now, but I'm guessing I 
should save my money and just live with it this year (again!).

I generally use corn glutton meal on the lawn but have a few really
stubborn 
areas along the driveway and sidewalk so I thought I'd use a stronger 
solution on those places.

I live just outside of Boston, MA (Zone 6 I think).

Thanks.