In any case, you NEED to test this out beforehand; you can't just wing it when you get to the real test.
Furthermore, understanding how the SAT is constructed can also go a long way toward helping you make these kinds of guesses. Knowing, for example, that the correct answer to many passage-based questions will essentially be a rephrasing of the passage's main point can help you identify the likely answer -- even if you can't find the necessary evidence to back it up and/or don't 100% understand what the question is asking. Granted you still have to nail the main point, but provided you can do that, you'll almost certainly be right.
So to sum up, if you're about to take a wild guess just for the sake of not leaving a question blank, you might want to think twice; but if you have good reason for picking the answer you're picking, you should probably go for it.