Bilingual city: Catalan and Spanish
There are two official languages in Barcelona: Catalan and Spanish.
Barcelona is the capital of Catalonia (Catalunya), therefore Catalan is the official language and widely spoken. Barcelona people speak both languages interchangeably.
Good English in tourist areas
In tourist areas you will be able to find people who speak - at least basic - English next to Spanish. In areas less frequented by tourists, people mostly speak only Spanish or Catalan.
No problem communicating in English
Communicating in English in Barcelona will not be a problem all together. It is a very cosmopolitan European city with vast number of tourists each year.