After visiting the library, I found these two gems: The Mount Diablo Guide & Mt. Diablo Wildflowers written by the Mount Diablo Interpretive Association. I just ordered them online and can't wait to get them in the mail.
Here's the story of how the Mountain got it's name, from pg. 20 of "The Mount Diablo Guide"
"The first reference to 'diablo' or 'devil' in connection with the mountain derives from an incident sometime between 1803 and 1806 (accounts of the year differ). A small Spanish force came to the area in search of runaway mission Indians. The troops got as far as a settlement of the Chupcan people in a willow thicket near present day Buchanan Field in Concord. They surrounded them, but the Chupcans slipped away during the night and crossed the Carquinez Straits to safety. The Spanish found it convenient to blame the devil for their embarrassment and called the place 'Monte del Diablo' or 'Thicket of the Devil'...Anglo settlers mistook the word 'monte' for 'montana', and fastened the name on the most obvious local landmark."