It's actually closer to the public lot than it is to the church. If you can't get in the public lot, continue down restaurant row (take a left out of the lot) and, just past Blue Martini you'll see the entrance to the lot on your left. There is a sign on the street close by Il Nettuno. If you get to the intersection, you've gone too far. And if you get to the church, you've gone way too far.

Very nice folks and, as another poster said, most restaurants will reimburse you for the parking fee. Plus, you have the benefit of the parking lot attendants watching over your car - they are paid employees, not just people off the street trying to "earn" a few bucks from unassuming tourists.