Fantastic city, Barcelona, spent last year living there and absolutely loved it. I don't do street photography but I'll give you my opinions anyway:
1. Would go in the trash for me.
2. Nice lighting, possibly crop in a bit from the top left and add a vignette to draw attention to the subject.
3. Awkward expression, no me gusta (or should I say no m'agrada)
4. The pick of the bunch for me because it seems to be telling a story, strong expression and gesture and you also have context with the clarinet.
5. I like this one too although it bugs me that the woman behind is sharper than the subject... I think this would look good in B+W
6. Doesn't do anything for me, perhaps partly because there's not enough 'looking space' to the left.
I think you have a good eye, keep at it