I've only ever been to the Japanese Tea Garden in January, and even then it has been one of the most beautiful places I have ever visited. There are walking trails around the flowers, monuments, bamboo areas, and some amazing views within the garden itself. I have been able to get some pictures of this place that look absolutely like paintings because it is just BEAUTIFUL.
Very much worth the small charge to get in. GO forth and visit this amazing oasis hidden within the hustle and bustle of the equally amazing city of SF, CA.