There is some good riding, so I've been told, out by the Purisima Mission. There's some other stuff too, but I think some of it is on the down low...
You're about an hour away from riding in the Santa Barbara back country off Gibraltar Road. Lots of options that way.
Montana de Oro and the SLO stuff isn't too far away either.
Four weeks in that area, you better bring a bike to have something to do. (I work in that area frequently myself, though not for four weeks at a time.)