You could also take a cab/van. That is what we always do. They are all lined up at the exit of SNA--waiting to take people to
Disneyland. You don't have to call them or arange anything. We have a large family, so we walk right up to the cab station and they signal for a "van" for us. Usually there is one right there--but a few times we have had to wait for under 5 minutes.
The price is really reasonable, and then we get the dirver's card to come pick us up at the end of our trip. It works out perfectly for us.