Hi Craig,
I would recommend you hire a car - never done public transport there so cant help with that. If you stay in the city it will take you about 75 mins to drive there on a normal Sunday.
With all of the expansion Menangle hasn't been great of late but most of that will be finished come ID day. I think the facilities are pretty good and it handles crowds well. Given the line up of racing you'd be mad to miss it!
There are 2 massive big screens at Menangle so race viewing is always good.
Mitch.