No matter how many times you visit Boulders Beach, seeing the African penguin colony in Simon's Town will always make you smile. The park itself is run by South Africa National Park service. There is a long wooden boardwalk on the outskirts of the park from which you can spot penguins (for free). Inside the park, you will pay a fee to walk down another boardwalk, right down to the beach where the penguins congregate. The paid boardwalk has the better view, so if you're bringing children or want the best photographs, this is recommended.
For an even closer encounter with these flightless birds, park at or walk to the far edge of Boulder's Beach. Proceed through the parking lot towards a tiny, wooden gate. Open it and you'll find a smaller pathway leading to the area pictured here. This is a public area, albeit very close to a few private homes. This turns into a pathway which allows you to get much closer, without any barriers to the waterfront, to observe the penguins in their natural habitat.
Simon's Town is easily accessible by driving or by train (last stop on the Southern Suburbs line and a short walk through the historical, naval town).