Your 1st century eh? What is your previous longest ride? If you've never gone over 60mi before, this adventure might become a nightmare. But if you have, well, go for it! Some points that may be helpful:
Food - bananas! No one has mentioned this. They come naturally wrapped, a few will fit perfectly in your jersey pockets, and you can go a long way on one with no risk of digestive problems. They also almost guarantee no cramps, if you keep your fluid levels up. (all that potassium you know)
Weather - if there is more than a 40% chance of rain I would scrub the mission. You don't want to do your 1st century in the cold rain. Even in California this will be miserable. Also, rain tends to increase punctures, unless it's the sort of deluge that washes the roads completly. There's also greater risk of crashes and visablity will be impaired. (this relates more to the fact that autmotive traffic won't see you as well and will thus be dangerous to you) The season is young yet, and there will be lots of other good week-ends to do this thing.
Other than that, good luck my cycling friend. There's nothing to compare with the feeling you get at the end of your 1st 100 miler. (with the possible exception of finishing your 1st running Marathon) Ride on!