I found La Cereria on the ole trip advisor, it was the 2nd highest rated veggie place (the first being rather more pricey and needing reservations) and we headed down the windy streets around Las Ramblas to check it out.
All tables were set up in twos and the capacity was only about 16 people but its a veggie place in Spain! Our waiter/the owner was doing everything single handedly so the service was slow at times but he spoke great English and had English menus for us.
I ordered the rice, black beans, and guacomole which was nice. Although it took me a while to figure out the sweet taste in the guacamole was banana, presumably to replace the cream as it was a vegan dish. I remained unconvinced about banana guacamole. Boyfriend got cannelloni which he liked, and a glass of red wine which he liked more. It all came to about 27euros.