To answer some of the questions that I originally posed:
1. Merit scholarships are announced in the summer. There's a very small pool of money that gets distributed after the school gets a better idea of who is attending. It's not really based on merit though-- you must qualify to received grants and loans from the school before you can even be considered for "merit" scholarships.
2. You can get an estimate by emailing the financial aid office once you have all of your forms turned in. They NEED your parents' 2012 taxes (filed this year) before they can tell you anything at all. UCSD does NOT match scholarship offers from other schools.
3. Current students say the estimates are very close, if not identical, to the real deal.
Sources: second look weekend talks and current med students.