It's very simple. It's just behind the swim complex in Katoomba. Just park in the carpark, and keep walking.
And yes, you can walk the whole length of the track. You could probably drive in if you could force the old gate, but that's probably not a wise idea.
It's a bit of a time-tunnel. Old start and finish lines, signage, old ads, etc etc.
Blue Mountains City Council would never re-open it. Cheap nasty little bastards don't even want to keep the civic pools open, and won't mow or maintain the sports ovals properly. So we can forget Catalina.
For what it's worth, it got its name from the old Catalina seaplane that used to live in the swimming-pool next door, in the years after WWII.