The park itself is amazing... the architecture and layout are incredible and a fine example of Gaudi's genius. It allows 400 people into the "Monumental Zone" every 30 minutes. You can buy tickets ahead of time so you don't make the journey up the mountain and then not get a chance to see this section.
Word of caution... it is a huge tourist destination with lots of crowds... if you can get in early or late in the day you might be able to enjoy it without someone stepping into every other picture you are taking.
The tile... plants, colors, and shapes, are definitely something to take in and enjoy. Going at a less busy time would only give you a better to chance to enjoy the area.More