I fly and rent weekly and am in SO Cal and DL almost monthly....so here is my take:
Rentals from airports are typically cheaper than local locations. Round trip is often cheaper then one way (but not always...sometimes one way can be the same price).
SD drive to Anaheim is only a bit over an hour and a half with no traffic. Closer to two and a half during afternoon rush hour.
To do the exploring outside of DL, personally I would want a car for all of that. Now, it is all about pricing it out. You have for factor in the following:
Airfare difference going into SAN vs SNA...then deduct gas cost of the drive
Doing a airport vs local branch rental
Doing a round trip vs one way rental
Hotel parking charges if any
Transportation charges from airport to hotel if you don't rent an airport car
Proximity of rental car site to your hotel and hassle.
Honestly will take a spreadsheet to calculate if it is worth it.
For me, it would be fly into SNA or LAX, rent a car the whole time and do a one way rental to SAN. Saving would have to be be in the hundreds for me to deal with separate transportation and local car rentals. How much time will you spend during the vacation coordinating transportation/cars and what is that time worth to you?
I will use a site like
www.kayak.com to research car prices with different pickup options then just book directly with car rental web site once I find the best deal.