Are there many halal places to eat in or around peoples square, Shanghai?

Yes, several good Hala restos are within walking distance, such as Yershari Xinjing Food at no. 819, East Nanjing Road, and Pamir Restaurant, at 205, Middle Zhejiang Road.

Well, I'd suggest you stay in the Le Royal Meridian, which is relatively a little cheaper than the JW Marriots. More importantly, it is closer to the metro station and the halal restos.