Don't think they are actually doing the drive-thru thing this year.
On Wed Feb 28, in front of the Clipsal 500 HQ, 191 Pulteney St, there is a Pitstop Challenge starting at noon, and also a Drivers Autograph Session, from 12-2. There is also the RSB V8 Supercar Luncheon at the Hilton that day, so I'm not sure which drivers will be where when, but I would suggest that if you can get to Pulteney St on the Wednesday that is your best chance of seeing any action before the event starts on the Thursday.