I am a frequent traveler and if possible use public transportation whenever I visit Europe. Most countries there but also countries as China and Japan have excellent public transportation. Trains and busses run frequently and timely.
When I first moved to Gilroy I couldn't figure out how to get to the airports in San Francisco and San Jose using public transportation. I stopped by the AAA in Gilroy asking for affordable public transportation options. They looked at me like they never heard that question before.
From Gilroy and Morgan Hill one can take the train to the airport. There are three trains early in the morning and at night on weekdays only. On weekday mornings trains 217, 221 and 227 depart from Gilroy between 6:07 and 7:20 am and trains 156, 268 and 274 return late in the afternoon between 5:11 and 7:49 pm. There is a free VTA shuttle between Santa Cara Caltrain Station and the San Jose Airport. There is also a shuttle available from the Milbrae Transit Center to the San Francisco Airport. That limits your options a bit unless you are willing to wait at the airport for several hours and you are traveling weekdays.
Shuttle Service from Gilroy and Morgan Hill:
There are other options which will cost you more. You may have noticed the SuperShuttle on 101 (as I do) a shared shuttle, which picks up in South County. Call them for more information at 800-258-3826 or visit their website.
Another option for shared shuttle service is South and East Bay Airport Shuttle. Contact them at 408-559-9477.
These are all choices in addition to limo service. Your last option is a rental car.