You can drift with an open diff but it will only spin the inside wheel, so its a bit lame and if you dont have much power it isnt really going to happen lol best of locking the diff up and having a crack at it!!
As i've heard S12's are brilliant drift cars, hence why i've got one.
What are the standard handbrakes like on them? i.e. do they lock up the back wheels enough? I'm getting a hydro handbrake anyway but would be nice to try the standard one first.
Here's a lil vid of me skiddin my old volvo on my second drift day at santa pod...
Personally, i'd suggest santa pod DWYB days if you just wanna muck about and get the hang of drifting.