I live about 15 min. from Ontario Airport. My sis visits from Virginia alot. She likes to have her own car while she visits. If you have AAA or a travel agent you can get great coupons for rental cars from Hertz. The site is in the airport and good cars to. My sis got a full size, seats 6 dodge caravan for $24.00 a day. Good luck!! Oh by the way, the food in this Airprt is good and bad
Last time I checked for someone Super Shuttle went from ONT to Disneyland.
The Ontario airport is GREAT! Its small, with three terminals. Two for flights and one for car rentals. There is tons of parking and the baggage claim is literally steps from the curb.
If you do decide to rent a car, know that while it SAYS that the car rental is "in terminal" you will still have to ride an airport shuttle bus to get to the car rental terminal.