If you are planning on staying in coastal San Diego, this would be the best airport to fly into.
If you are planning on staying inland (east county) San Diego, this would be the closest airport, although San Diego airport is close by too. It is always good to check to see which fare is cheaper.
You can sometimes find cheap tickets flying into this airport. Just another option!
This is the farthest airport, but you probably find the cheapest flights since it is a hub for a lot of airlines. Please know that LA traffic can cause delays in travel, so plan accordingly.