We decided to have our wedding in northern California because we wanted to share what we love about where we live with our families and friends. While we still have strong ties to the East Coast (it's where we grew up, and our families still live "back east"), we've found the San Francisco Bay Area to be an ideal spot for us. Al has lived here since 1991, and Lori moved out in 1996.
The Bay Area is a beautiful place with widely varying "microclimates"—that is, the temperature can range from 50 to 90 degrees on any given day depending on where you are, the sun can be shining brightly in one neighborhood while another is fending off a driving fog, and a strong headwind can be blowing northbound cyclists on the Bay Trail off their bikes while folks in San Jose would give anything for a breeze. The trick is knowing what the prevailing weather patterns are in the spot you plan to be in. The Peninsula is generally warmer than San Francisco and usually a bit cooler than San Jose and the interior valleys. Areas bordering the Bay are often windy; the wind strength increases as the day goes on, and blows from the north.
September and October are arguably the best weather months in the Bay Area, mainly because the bone-chilling fog that turns summer tourists blue disappears, and the rainy season (which starts in November) has not yet arrived. Most areas are warm and sunny, especially on the Peninsula. However, we recommend that you bring a sweater or jacket just in case, and layered clothing is always a good idea.
San Francisco International Airport (SFO) and San Jose International Airport (SJC) are roughly equidistant from the ceremony site in Atherton, so which airport you choose to fly into will depend on which route offers a cheaper fare and what you'd like to see while in the Bay Area. If the wineries of the South Bay interest you*, you'd like to see a Sharks game while here, or if you are staying in one of the Palo Alto hotels, San Jose is a good choice. If you're staying in Redwood City or San Francisco, want to see "the city" (there are obviously many cities in the Bay Area, but when people say The City, they mean San Francisco), Fisherman's Wharf, the Golden Gate Bridge, etc., SFO is a better option. It's 15 minutes south of San Francisco (and 15 minutes north of Redwood City) without traffic.
United Airlines flies to both SFO and SJC, as does American Airlines; with AA, the fares are often cheaper at SJC than SFO. Southwest Airlines flies to and from smaller airports (including SJC) and usually has inexpensive fares for last-minute purchases, and even less expensive fares when tickets are booked ahead or on the Internet. ATA, Frontier, and America West also tend to have cheap cross-country fares.
Note that if you are flying from a U.S. city east of San Francisco, it is possible to leave in the morning and arrive in the morning because of the 3-hour time difference. For example, United has a flight that leaves Baltimore-Washington International Airport at 7:20am and arrives at SFO at 10:00am. Similar flights may be found from New York and Boston airports as well. While this is very convenient, it also means that you're in for a long day, so plan for a nap if you can. The opposite rule holds true when returning home: you'll lose time rather than gain it. A flight leaving at 10:00am or 11:00am will arrive on the east coast at anywhere from 6:00pm to 9:00pm, depending on your exact destination and the number of stops.
*Yes, it's true: Napa and Sonoma aren't the only places with wineries, though these north-of-San Francisco areas are the best known. If you prefer Napa's vineyards to those of the South Bay, SFO is a better choice than SJC. You could even try for a multiple-destination ticket that lets you combine a flight into or out of Sacramento (SMF) with one into or out of SFO or SJC.
If you want to see more than just the wedding while here, you'll want to rent a car. Both SFO and SJC host all the major rental car companies, as well as a few minor ones. If attending the ceremony is your main goal, the hotels in Redwood City, Menlo Park, and Palo Alto are close enough to take a taxi (you'll need to call ahead, however, if you're staying at a smaller hotel; taxis only queue up at the larger hotels). Caltrain runs between San Jose and San Francisco and can be a good option for sightseeing on weekdays, but they've eliminated weekend service for the next two years due to construction.
Directions to Holbrook Palmer Park