lose the negative attitude... that'd probably help a lot. You've been there 3 days and already you're judging it. If you think the only thing to do there is to go to Rundle Mall, then you're sadly mistaken. Adelaide is much better with friends, as you'll find once you make some. The beaches, the national parks (Morilata and Waterfall Gully) are great. The bike paths are fantastic. Other parts of the city are worth exploring and it's nice to get out of the city too and check out McLaren Vale or anywhere else. I have been to Adelaide many times and I find so much to do when I am there.
Being Asian, I think you're "China guyz" comment is not worth mentioning, but I think you've seen a very small section of Adelaide. Adelaide is largely anglo-saxon/european and white. There are far less asians, africans, latins and middle eastern than in any other major city in Australia (or around the world for that matter). Get some perspective, make some friends and try and think positively. If you already have a chip on your shoulder about the place after just 3 days (and thinking Rundle Mall was "it"), then you'll never survive!!
See Demographics: http://en.wikipedia.org/wiki/Adelaide