I printed 20x30's from my old 10d camera. A 12x24 will be fine, go for it! Be sure you have a sharp image to begin with, and also carefully go over the file at 100% or better looking for and correcting any sensor dust or other things you want to retouch out. These spots are always glaringly obvious in prints, but not seen sometimes on smaller screens at 33% or whatever.
Rodney-D200, D300, 12-24, 17-55, 70-200 etc.