Where is the best place to visit during end 27 apr to 5 May? White cloud mountain or yuexiu park ?

Well, either can be ok. If you have enough time, I suggest you visit both of them. At the mountain, you can look down the whole Guangzhou city. Natural scenery can be enjoyed there. It is also worth to experience the cable car. The latter is a park for free. Plants, flowers, boats and some humane buildings are available for fun.