Hey man
Im live in Barcelona and let me tell you what i know.
With the clubs its mixed, the really good clubs with the best weed will not let you in a million years unless you got a friend.
The shitty dodgy russian mafia and the like owned clubs will most likely let you in.
From my experience the best clubs are in the Eixample area.
I dont go to the clubs in the city centre much but i do hear there's a couple of decent ones, 420 is one of them.
Expect at least a 10/15 strain menu, a ridicuoous hash and extraction selection are common too. If you grow your own you will be EXTREMELY disapointed with the average quality though. Very few clubs have weed the way i like it.
Lahadaextranjera has membership to a lot of clubs, i dont have as many. Shell probably be better to ask about it really.