I had difficulty finding official confirmation if the County Office building had extended hours for ballot returns this weekend through to Tuesday. I went down there today, and indeed they do. I asked about the hours, and wanted to share them in case anyone else in the neighborhood was in the same boat.
Sounds like today (Saturday) they are open until 5pm, then Sunday 11a - 7pm, then Monday and Tuesday until 8pm.
The Ross Street entrance of the building has a lane blocked off again so you can run in without having to park, the ballots are accepted in the lobby.