I did this on the cheap and had an amazing experience. If you don't want to spend loads of money on cable cars or queuing then keep reading.
I knew I wanted to see the views from Mount Montjuic and debated how to best do this without all the queues and cost. At the time I was several miles away so rode on the underground, jumped a few lines which took me to the station called Paral. El and I was able to surprisingly take the finacular half way up the mountain, for €2.40 one way ticket. A finacular is a little train that runs up and down. Whilst you don't get the views like you would from a cable car, you do see fab views from the mountain. The locals tend to use the finacular whereas the cable cars are geared at tourists. There are two cable car options. The first is called port cable car, which takes you from barceloneta Beach to the same place as the finacular. Once you get out of the finacular you walk around the corner and can get the second cable car further up the mountain. Just a note, the finacular is not suitable for wheelchairs, as a number of steps. For me, once I left the finacular I walked up a little hill, through a pretty park, I then found a sign telling you to go to a viewing platform. I walked up and found a lovely viewing place with a kiosk for refreshments. The viewing place was amazing. I then walked down the mountain towards the magic fountains. I went up around 6pm and was up there to see the sunset and stayed for the magic fountain display.