As I mentioned in my previous post, the dealings between thieves, the bars, and the police is a scandal ripe to be unearthed by some enterprising journalist looking to expose the odious symbiotic relationship between the three. But, until that happens and we start claiming the streets back from the scum who prey on the innocent people visiting our city, you need to know how to avoid them. My friends at At Home: Barcelona have some useful advice, but I also want to take a minute to offer some suggestions on how not to get robbed, while also seeing some parts of the city and its surroundings that you probably wouldn't have otherwise.
The thing to remember about thieves is that they go to where the tourists and crowds are. This means - if you wanna go for a swim - don't go to Barceloneta and Port Olimpic, unless you have someone watching your things at ALL times. However, if you hop on the train at Plaza Catalunya and take it north for half an hour to las playas del Maresme, you can find wider and more spacious beaches like Cabrera del Mar where the pickpockets generally don't go but the locals do, so you can enjoy and relax in the sun and cleaner water, while eating and drinking at the cheaper chiringuitos.
Rambla Catalunya, escaping the heat and the thieves while you stroll under the shade of the green trees and see some of Barcelona's more impressive buildings, and if you're feeling tired there are plenty of restuarants and bars with terraces to stop and grab a drink or something to eat - just don't leave your belongings on the tables. Finally, if you're coming from the Sagrada Familia or Parc Guell, walk into the city - it's down hill and Barcelona's not a big place, and you'll avoid the metro.