Marilyn will delight you with her seemingly endless knowledge of San Francisco's rooftop gardens and the rich history of downtown high rise buidings. I was in a group of 4 and we walked just under 2 miles over about 2.5 hours. It was a lot of fun and I would recommend it to tourists and locals.
The tour was a great way to see the city from another perspective. As a native San Franciscan, I've passed by these buildings my whole life without even realizing they had gardens on the roof! Marilyn also knew great historical facts about the city and had great little stories that made me look at downtown in a completely different way. She's a very pleasant guide and knows her stuff!