If you want use mobile phone, ensure your mobile is unlocked for use in China if taking your own. Also consider buying a data SIM card in China for constant network access away from wi-fi hotspots. If buying 3G SIM cards, China Unicom offers almost twice as much data as China Mobile.
The official language of China is Standard Mandarin, which is mostly based on the Beijing dialect, known in Chinese as Putonghua. Shanghai, Beijing, Guangzhou, and Shenzhen do have a higher proportion of English-speaking locals.
Wi-fi accessibility in hotels, cafes, restaurants and bars is generally good. The best option is to bring a wi-fi equipped smartphone, tablet or laptop or use your hotel computer or broadband internet connection. Many internet cafes only accept customers with Chinese ID, barring foreigners. In large cities and towns, the area around the train station generally has internet cafes.