HAHAHAHAHA sorry, just had to laugh at the thread title. A lot of people shall take offence to that, me included.
But on a more serious note:
1. York doesn't have many clubs and such, but if you want a good night out, then you can have a good night out. I'm at uni in Newcastle, and in comparison there aren't that many clubs or even student nights, but its still a good night out - especially since everything is so packed together and you don't have far to go to get to places. I don't know much about the uni stuff however (I'm a resident)
2. Well my opinion on ethnic diversity is that its limited, VERY limited. But if all your bothered about is "food" then you'll have no problem. As far as I'm aware, there have been no major incidents (in fact, my asian friends have had more hassle moving away from home) and everyone is generally accepting, but maybe that's just from a younger persons perspective?
3. The campus is very pretty (in the surrounding area) though some of the buildings leave a little to be desired with the "concrete" theme. But its all set out around a lake with DUCKS!
4. Don't know much about the uni, apart from that they don't take you without Chemistry (at least at AS)... from personal experience