Do people in Barcelona speak Catalan instead of Spanish?
Spanish and Catalan are both official languages by law here. Normally you will find that people will converse with you in whatever language you speak with them in, on the street (I suppose it depends on your Barrio) I usually hear Catalan more often.
Of course, there have been some very rare occasions where you will find someone will continue to speak in Catalan, this isn’t usually done is spite and I believe it is more to do with comfort, however you can always politely ask them to speak in Spanish if you do not understand Catalan, and I’m sure that they will oblige.