Guangzhou is definitely worth a couple of days. It's a very interesting mix of a city (old/new, rich/poor, Chinese/Foreign Asian/Western), and I just enjoy the energy of it (it feels more natural than the HKG equivalent).

Not sure about what hotel prices look like during the fair, but I was there last week and the foreign chain-hotels looked a bit overpriced to me, so I tried the Garden Hotel. Booked what they call an "Executive Suite", which was a phenomenal room (92 sq. m., floor-to-ceiling windows even in the bathroom, 3 LCD TVs, a host of L'Occitane amenities etc etc etc), and only cost me 1286 RMB including a massage treatment, a great breakfast, and 500 airline miles!