Ocean Beach Pier is the longest concrete pier on the West Coast. The pier is a wonderful place to catch the sunset and take amazing pictures (do a Google search, the pictures are breathtaking). We visited the pier in early January so it wasn't as crowded as I'm sure it is in the summer. Street parking was free. The pier has a decently long perpendicular section at the end so there's plenty of space for people to gaze out at the ocean or back at the coastline.
Ocean Beach Pier is probably the closest you can get to watching surfers in action without getting wet yourself. At least when we went, the waves were breaking right underneath us. There's also a cafe on the pier which has some crazy pictures of when the waves have washed over the pier and obliterated the cafe (Google these too).
I doubt we would come here to hang out on the beach, as there are much more scenic beaches in San Diego, but we will definitely be catching many a sunset from this pier.
Click here to see more of our pictures from Ocean Beach Pier.