Why not? Basically, preregistering just gets most of your hospital paperwork out of the way before you come in to deliver. This way, the docs and nurses have your info (employment info, insurance documents and the like), and your file will be all ready to go when baby decides it’s time to make an appearance. It shouldn't take too long, and you might even be able to do it over the telephone or Internet.
If your hospital allows preregistering, we say go for it — you probably won’t be too excited about signing forms and digging for your insurance card once you’re in active labor. (Think your partner can simply deal with the forms? Maybe so, but that means you'll be missing his support while he's busy with the paperwork. It can also save you from potential insurance headaches down the road — mistakes are more likely if you register at that last (crazy) minute.