Of course, he didn't say it - http://www.snopes.com/quotes/twain.asp , but still.
Among other things there, Muir Woods is truly amazing - http://www.nps.gov/muwo/
I second your recommendation to visit the Bay Area, but for perfect weather it's hard to beat San Diego. http://www.wundergro...its=none&IATA=SAN
:-)
Cheers,
Scott.