Same problem with everyone - UK iPhone 4, upgraded to iOS 5 in Shanghai and now Chinese map with no Pin Yin. I re-downloaded and restored it under UK VPN and UK SIM in Shanghai with no resolution.
THEN I landed in Hong Kong today, switched to my Hong Kong SIM card and voila, English maps and Pin Yin Chinese!!! I hope it stays this way when I fly back to Shanghai this Friday.....will report back....