Go to www.sfarmls.com and put 500 Masonic into the parameters and the information will come up. It should show open houses. If it does not, then you can contact your agent or any others and ask.
For future reference, you can also subscribe to my weekly newsletter which lists via links Open Houses, weekly sales figures, information on districts, mortgage rates and more. Just email me at firstname.lastname@example.org and I will add your name.