This is a little place I found some years back wandering the little streets beside the Rambla. Kasparo is tucked away in a corner on a leafy Square just minutes from The Rambla and just up the road from The Boqueria.
It has an eclectic menu with something to suit everyone's taste, even a fussy vegetarian like me. It is an informal and friendly place to grab a coffee, a quick bite or something more filling. The waiters/resses tend to speak English but if they don't they'll soon grab someone to help you.
The humus is served with warm pitta bread, as it should be, and they have a version of Patatas Bravas which they have named Patatas Kasporos.
So after your visit to the Boqueria, and the almost obligatory walk along the Ramblas go check out Kasparo - I think you'll be pleasantly surprised.