The one that's $2 all day is on Washington (the care entrance) and there's a walking exit 2 doors down from Ops. It's a brick one, and the entrance is a big ramp that leads up off Washington.
SRK is back up if you need more details. That will definitely be cheaper than the one on Maynard.
Depends which garage. One of them is $2 for all day (the new one) from what I understand. I may be wrong though.
EDIT: Info for the new one is in the SRK thread. I never posted it here and I don't have time to copy it over now.