Les Quinze Nits in Placa Reial is really nice! Placa Reial is about halfway down las ramblas and full of bars/restaurants so there is lots to see! Les Quinze Nits doesn't take reservations so don't be put off by the queue outside - it moves really quickly as there are lots of tables. There is a website if you google it I can't post the url.
The bus turistic (open top bus) is a great way to get around the main sites - you can then hop off whenever you come to something you want to explore further. Your hotel will probably sell tickets for this and advise of the nearest collection point or if not then you can buy tickets and get it from outside El corte Ingles by Placa Catalunya. Again there is a website if you google it, I can't post the url.
Barcelona is one of the best cities in the world - enjoy!
Goggles