We went down the square around 2.30 and the police although clearly visible, kept a relatively low profile (by their normally heavy handed standards). Around 4.30 there was a change in mood and atmosphere. More and more riot vans and police started to appear and the balaclavas started to be pulled up. As we were moving towards the edge of the square, I actually saw one copper loosening up his wrist by having a few practice swings with his baton. That was our signal to leave.
Went back to the apartment and then caught the Metro to Les Corts and didn't have any real problems from there and getting in the ground. Then again, we did have a small child and his grandad with us, so perhaps they were a bit more sympathetic. e.g. They let us take the lift up to the gods. They even let us take our drinks to the seats, 2 bottles of water and a coke.
Inside the ground, the coin throwing was shocking. I saw a bloke (late 40's) on the row in front of me do it in the first half. Politely told him he was out of order. He just shrugged his shoulders, but at least didn't do it again. Even when we were awarded the penalty a load went over the fence. Even more when it was saved.
We left our seats on 85 minutes and were allowed to leave, probably because we asked nicely and had the young kid with us. Walked back to Les Corts Metro and got on it without any problems. By the way, passing a ticket back is a common practice. All four of us used a T10 (Journey) ticket so did the pass back every tube we got on.
I've been to Barca x 2, Madrid, Santander & Villareal watching City. Every time has been chaotic at the ground. The Spanish police are just not used to dealing with large away followings. They also think that English football fan equates to hooligan. Which makes for a bad combination. The sad thing was that last night, some of the fans in the away end and in the square (twatting a ball at peoples windows) gave them the reason to think that way.