Is English widely used in Beijing? In terms of road signs, on public transport, etc.

Well, dear. Please do not worry about it. Peking is a modern and international city, it is very easy for a foreigner to explore it on his or her own. Local people are very friendly, so it is very safe to walk on the street to enjoy the beauty of the city on your own. In major places and on transportations, the signs are written in bilingual ways. If you want to know more information about this city, please refer to https://www.travelchinaguide.com/cityguides/beijing.htm. Hope you can have a good impression on this city.