I don't know of any "gypsy dancers" in Barcelona, although I could be mistaken. Perhaps the dance to which the person was referring was the "Sardana" dance which is a traditional catalan dance. I have never seen it on my trips to Barcelona, but I have often read about it and I've seen it on television. It is performed in front of the cathedral in the Gothic Quarter on Sundays.
You can read an earlier post with a description of it by clicking
here . Also, there is a You Tube video at
this link . If you ever watch Samantha Brown's "Passport to Europe" show, she participates in the Sardana dance during the episode she filmed in
Barcelona .
Enjoy your trip!