We spent our first night in Barcelona rambling La Rambla last night from dusk to dark. We treated our "safety" as we would at home. For all the teeth gnashing on this forum about the gauntlet of pickpockets, there's no need to be anxious or fearful... Just aware. It felt like walking through Rome at night -- or Paris or New York or San Francisco. Leave wads of cash in your hotel room's safe with your tablet, passport, and prescriptions. In fact, in two places we stopped the clerks asked for tarjetas (cards) since they didn't want to make change.
I agree! We were in Barcelona in late April. I appreciated the heads up about pickpockets as we did take some extra precautions, but we walked around quite a bit in the old part of Barcelona and encountered no issues. We didn't see any funny business either, and believe me I was on the lookout because I tend to be a bit paranoid. I didn't feel uncomfortable in Barcelona-Sants either. I was expecting chaos there. All in all I found the city to be safe and comfortable. Just be smart and you'll be fine.
We were in Barcelona in November and found La Rambla not too crowded and felt safe. April and May are also in low or shoulder season. People who visit June to August probably have a different experience.