Beach Club Villas are a DVC property. When you check in the desk will already have your room assigned. If it is not ready the desk will give you a phone number to call at 4:00pm. When you call the phone number and give them a password they will tell you your room number. So yes, you can check in, check you lougage with the bell man, and go swimm at SAB. You room cards will already be set up with your room number, you just won't know what it is until 4:00pm.
Have a great trip.