A big part of the problem with Cuba is that there are several laws implemented at different times which all add up to the Embargo. The president could push to drop the embargo, but it's congress that would have to schedule a series of votes and repeal all the stuff.
It's my guess that congress won't bother to do this as long as there is any possibility of negative PR.
Also this: Castro has taken every opportunity to give the -FU- to the United States on the issue. In '93 for instance, the republican congress limited the amount of dollars Cuban nationals could send back to there families in Cuba - Castro responded by making the US dollar illegal currency in Cuba. It remains to be seen what Raul will do when he takes over, but he's not exactly young either (76).
Anyway, it is an inane policy, and it's been put in place in such a way that I think it would take more than a presidential order to take it apart. Congress might have to take an actual vote and go on record with actual opinions and such (insert sarcasm).