Travell time from Guangzhou to Hong Kong Airport

Ill be leaving from Hong Kong Airport flying to South Africa - flight departs at 18h00. I wanted to know if I would have enough time to go to the Canton Fair that morning and still make it in time for my flight. I'll be staying at Xiancun Road, Zhujiang New town, Tianhe District in Guangzhou. I also wa\nted to know how that is from the Canton Fair and what the best way to travell would be.