Hi,
Well, I live in Adelaide, and there is lots to see and do here. Pity you can't change your wife's visit to November as the Adelaide Classic Rally is on then (like now...)
March is a pretty good time here, but it can be hot, and the sun will burn you to a crisp in about half an hour, so bring your hat and lots of susnscreen <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> Without knowing what you like apart from 968's here are some things you could get upto in Adelaide, come march:
* Clipsal 500 street race is on 1-4 March - this is the local flavour of tintop racing with local Ford and GM V8 powered appliances.
http://www.clipsal500.com.au/
* Keep an eye on the SA Porsche club website for the 2007 calandar:
http://www.pcsa.asn.au/
* Adelaide Fringe festival is on 8-31 March. Lots of entertainment here, some of it good <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />
http://www.adelaidefringe.com.au/default.aspx
Generally, there is plenty to see here. Adelaide is home to Australia's biggest and bestest wine industry, with plenty of charming cellar doors within an hour or two's drive from the city. Google for the Barrossa Valley, Clare Valley and Maclaren Vale wine areas. It also sits on the edge of the outback, so if you are after a desert experience, this is a pretty good place to start from.
Hope that helps...
Michael