It's good to get the Sims card, since Barcelona city wifi is not reliable:
On my recent trip to Barcelona June 2016, I went with Vodafone and had a great experience. I forgot to pick up the sims card at the airport, as advised on other forums. Unfortunately, when I went to Corte Ingles at Placa Catalunya (the biggest one, there are three of these stores within a block of each other, and a forum had recommended going there), neither Movistar or Vodafone said they sold the Sims card.
I was able to get the sims card at a Vodafone store near my hotel. 10 Euro for 1G, 15 for 1.5G, or 20 for 2G. You need to bring your passport. I was worried I needed to go to a store near tourist locations, but the location I went to was not necessarily in a tourist location. I will give the address, but definitely check store closest to you. Rambla de Catalunya, 87, 08008
I did receive some texts from Vodafone about promotions, but nothing over the top. Helpful staff, just remember to sign in at the kiosk in the store so you get served in order.