Hi there,
One of the best ways to get cheap flights to San Diego is with a vacation package, epsecially since you're traveling with the family. With a vacation package the airfare to San Diego, airport shuttle,
hotel and tours will be covered.
If you're just looking for
flights, discount "no frills" airlines are another cheap alternative. Also, try and book the flight during the week. An early or late flight can also save you money.
Hope this helps
Vacationbuddy