After looking at HappyCow for suggestions we decided to start with a little place called Vegetalia. This started our adventure with Spain and "open hours." In the US I was used to shops small and large having their posted open hours and those being fairly accurate give or take a few minutes. Here it seems you're lucky if they have posted hours, those hours are merely suggestions, and they will almost certainly be closed for siesta and on Sundays. So we had to walk by Vegetalia a couple times over a couple days before we hit it open.
Vegetalia is not strictly vegan so be sure you talk to your server. As is the case all over Spain, they may not speak English but they know what vegan means here (you might get blank stares in other restaurants). When we went our server did not speak English and he did not know for sure which items were vegan but he was super friendly and more than happy to consult with other staff to check on veganness. Don't speak Spanish? no problem! We don't either. Vegano is Spanish for vegan when you're lucky enough to encounter people who know what it means. This isn't so different from the US when you think about it. How many times have you asked for vegan and maybe even spelled it out, "so no dairy, eggs, honey, etc" and received a soup with chicken stock or a sandwich with traditional mayo on it? So at Vegetalia, if you don't speak the local language, simply point to what you are interested in and ask "Vegano?"
So let's actually talk about some food yes? We were in the mood for burgers so that's what we went for. Expecting a burger on a bun, we were surprised to receive a burger on a pile of salad with wholesome brown rice. For me to eat healthier why don't you. In all seriousness though it was very tasty. The brown rice was lightly seasoned and ever so slightly sweet. The burgers were both very tasty. Lex ordered a seitan based burger (I'm sorry to say I forget the flavor) and mine was seaweed tofu. Again, not all the burgers are vegan so be sure to ask.
Really like the burgers and maybe need some other bits? Well Vegetalia also stocks a small shop area with a mixture of items including some of their own brand foods like the burgers and tofu. They also stock a small selection of books. I didn't peruse these due to my abysmal Spanish and our backpacking/travel lightly state. The Vegetalia brand can also be purchased in other supermarkets around town like El Corte Ingles.
Vegetalia offers a little of everything from the Menu del dia, a set menu for 9.90€, to a simple coffee and juice bar. Sit at the bar or grab a table. Snag the local animal rights paper, Anima Naturalis, off the rack to remind yourself you have local allies and to look for other cruelty free businesses to visit in Spain. Definitely visit Vegetalia when you're in Barcelona. It's cute, tasty and friendly.