When to go
You can photograph Seal Rocks at Ocean Beach during any month of the year.
Before visiting, be mindful of and try to avoid fog, which can roll in any time of year—especially in the summer. Fog will make this composition difficult because it always hits this part of San Francisco first.
During sunset, the sun will dip behind Seal Rocks, creating some nice dynamic lighting conditions.
Field tips
Do not leave anything in your car when you park. Break ins are common in San Francisco, especially in this area.
I recommend using a wide-angle lens to photograph a similar perspective of Ocean Beach.
You can also shoot with a telephoto lens, which can be used to capture how long the beach is as it extends south down the coast.
Bring a friend with you to have a prominent focal point in the shot. It'll also add a sense of symmetry to place them in the middle of the photo.
Look for other rocks to use as foreground to frame your image.