How is Barcelona for non-smokers in terms of finding good restaurants that are totally non-smoking or have clear designated section for non-smokers ?.

By "good" do you mean "upscale" or do you mean "tasty food"?

In general, Spain is about where France was 15 years ago as far as smoking is concerned. This is not a criticism, merely an observation.

We found two huge tapas restaurants that had great tapas and no smoking. One, on the Passeig de Gracia, near the Casa Mila, was called Tapa Tapa, the other, whose name I do not remember, was on the same street between the Gran Via and Plaza de Catalunya and featured Basque Tapas. Otherwise, smoking seemed universal, but my experience is very, very limited.

Sit outside if at all possible.

We got into one of my favorite restaurants in Barcelona because we are non-smokers and the only place open was the non-smoking section. It's La Dolca Herminia at Magdalenes 27--2 blocks towards Ramblas from Palais de la Musica. It has mostly a young crowd (when we're not there ) and is very inexpensive.

Starting Jan 2006, restaurants and bars above 100 sq meters surface must have a separated non-smoking area, while those below can choose to allow smoking.

All places must indicate at the entrance if they allow or not smoking.

In practice the law is not enforced. About 95% of the places below 100 sq meters allow smoking, and many of the big places ignore the law. Your best bet is to choose big places and call before you go.