Manhattan Beach! I love running and biking along the boardwalk. The setting couldn't be more perfect, you get a panoramic view of the ocean, a wonderful cross breeze and a boardwalk that is flat. The bike path is separate from the running path so that there is less congestion on days when it's crowded (weekends). Also there are benches and water stops lining the strand so that if you don't have water with you, you can easily take a break, relax and enjoy the scenery and the beautiful ocean view and sunsets.
I would definitely recommend spending a casual sunny weekend afternoon along Manhattan Beach. Great local restaurants, coffee shops and yummy eateries to ride or run to.
Don't forget, the Sea View Inn has free bicycles for all our guests!