Poble Sec is a perfect location for restaurant/bars, Montjuic park, the metro green line which takes you to all the major attractions.
We walked to the Magic Fountain and back for the show one evening easily.
Everyone warned us about pick pockets but we never felt hustled or threatened , I find the London Underground much more stressful!
The apartment is away from the main road and it's one way so there is no busy traffic noise, you just get the buzz of people enjoying the evening outside in the nearby square and bar. The windows are double glazed so you can shut the noise out if you want to and has air conditioning if needed - we didn't as it was a beautiful English summer temp when we were there.
The lift to the fourth floor was clean and efficient and a welcome bonus after a long day exploring the streets!
We loved it, loved it, loved it - Barcelona is a must and this apartment in Poble Sec will do everything that you need it to.