Always ALWAYS bargain with the dealer. Any good used car shopper will tell you that the sticker on the window is for suckers!!
Here's my reccommendation - offer them $18,000, and then bargain from there - you might get laughed at, but you also might be really surprised by what price you get it for.
If that car has 11K miles, then they probably raped the poor guy who traded it in. Most times you can get a used car for a few hundred over what the dealer paid for it on trade-in. So, guess at $17,500 - $18,500 dealer cost, and don't pay much more than that
Just my 2cents