If you're thinking about visiting the Parc and getting there by metro, I would recommend taking the metro to Vallcarca instead of Lesseps, because it's less of a walk from the station and there are outdoor escalators that take you up to the park if you take the Vallcarca exit. From there on, it's all downhill, so it's less tiring, even though you might feel like you're not taking the "conventional" route by not entering the park via the front entrance, where the famous mosaic dragon is.
The park is definitely worth visiting. The mosaics and the gingerbread-house-like buildings are so cute, and there's no admission charge!