Baby Gear Rental Companies
You can rent cribs, carseats and more at your destination from a local rental company.
California has some of the toughest carseat laws in the country. Children must be secured in carseats even in a taxi until they are either 8 years old or 4'9" tall. Consider using public transportation or renting/buying a Travel Car Seat. At this writing, none of the major airport shuttle services provide carseats for customers.
Here are a few local limousine companies that will provide a car-seat when they transport you into the city from the airport. Be sure to reserve both the limo and the carseat in advance, and reconfirm the reservation on the day of travel:
A Better Limo Service
A Grand Limo
A Quick Limousine