Hey buddy – if I can help, just fire me an email….
I rode there last year and am riding there again this year in September.
You will need to get a Day Pass to ride Tamarancho from Fairfax Cyclery ($5), but if Charlie is around he will certainly show you where to go etc. to get this, but it is pretty easy to find on the main road.
This is the link showing some of the Tamarancho stuff we did – LINKY!