With some tricks you might be able to achieve it, like display:none; for the acronym tag in the print css and place the full name behing the acronym in a span with a class that places this tag somewhere outside the screen, e.g.
<acronym title="National Basketball Association">NBA</acronym><span class="hide">National Basketball Association</span>
some people recommend to use display:none in this case as well, or other techniques. Don't know whether this one is the best.
That should do the trick. Hope that makes sense, It's pretty late and I'm a bit tired...