While my mom was in San Francisco this past weekend we ventured over to Angel Island. It is a short ferry ride or drive across the Bay. Being there you would never know that a major city was just a short swim (I joke, you wouldn't make it because of the freezing water) away. It also didn't hurt that it was an absolutely stunning day--the kind of day that makes you all-the-more proud you live in California.
The views from the island were beautiful and the sun was hot (I have a very red nose to prove it)
Enjoy! Here is information on the island and how to get there.