La Rambla is to be sure a tourist mecca, therefore at heightened risk of pick-pocketing. That said, I walked up and down it many times during my ten days in Barcelona, carrying a Contax G2 and a full complement of lenses and never had a problem. Don't be afraid - just be sensible and you'll be fine. Don't walk around gawking like a stupid, unaware tourist and you'll be fine. Not far from La Rambla is the old medieval neighborhood where the art galleries are located - if you're there, take the time to wander over and check them out. Even though it's a (relatively) small scene, it's a lot more enticing than the New York scene, to me - I liked a lot more of what I was seeing.
Bear in mind that ARPI has two locations on La Rambla - one at the very bottom of La Rambla, maybe a block if that from the Columbus monument, and another one, on the same side of the street a block or two further up. The big ARPI is the one closer to the Columbus monument. I don't know about the Spanish camera market but to me their prices for used camera gear were QUITE high, but they could be indicative of the european camera market in general.
