Hi Ilia,
I live in Barcelona and I can tell you that there are really good professional labs here (Barcelona is full of artists, designers, architects...). I use EGM (you can visit it at EGM.es to see details). They are not expensive by Barcelona standadards (not sure if our prices are cheap in general).
Colour film (chromes or negative) usually develop in one day but B&W may take two days as they send them to COPIA, a specialized B&W film. You could send them directly and save some time but i prefer to use only one lab.
Foto Casanova, now with a new store really in the middle of the city (casanovafoto.com) is a must. They have a lot of new and used equipment and are really friendly. And i think they also develop film so you could save going to EGM (which is in the upper side of the town -but Barcelona is small-). Ask for Emmanuelle, a helpfull photographer who speaks english, italian spanish, catalan.... and knows almost anything.
ARPI is a big store in the middle of Las Ramblas but I have been there plenty of times anf they fail to being helpful. Just they seem to do you a favor selling you something...
Very very nice city for photographers!
We have accquired a good reputation for being a dangerous city for tourists. I think we are not different than any other touristic place. Just beware your belongings and try not to appear as lost tourist!
Have a nice time,
Jaime