In reply to Jay83:
This is the main forum, it's quite active and visitors are always posting for partners:
https://www.facebook.com/groups/rcibm
It has been a very wet and cool spring/summer but it's starting to dry out and most places are fine now. Just one day is a bit of a gamble though.
You can get a train from Central in Sydney to Katoomba, Blackheath and Mt Victoria, the three main towns for climbing. Beyond Mt Vic the line has been disrupted lately. Some crags can be walked to from the train station but most you need a car.
For those grades, Mt York, Mt Boyce and the Sunbath area near Medlow Bath. Upper Shipley might also be OK and is one of most popular crags in the mountains.
Note that in the Blueys, as in all east coast Australia, many campsites are busy/full nowadays so take into account if you need to do that.