You can change your dollors at reception, however there is a little shop next to the internet cafe and the bar ( think its in the south tower ) where you can change your dollors. This is under the counter and not official but you will get a lot more than in the reception - basically whatever you feel happier with, we changed it at both being honest as the shop opens a strange times.
There is a big big shopping centre about 10 mins away in a taxi, costs about £2 to get there. Lots and lots of shops in there, lots of place to eat ( subway !!!, hard rock cafe, mcdonalds etc ). Food is quite resonable but the shops are not particularly cheap - in fact i thought they where expensive. Good place for a look around and its all air conditioned........