Sorry, work + back to school rush - Trulia took a backseat.
You know my answer - Marin, so I won't repeat. But I have to be honest, i am not familiar with Lafayette.
I do know that a lot of families are willing to either commute and/or pay a premium to live in Marin and they won't move away once they are here unless they absollutely have to.
I think that says a lot.