Have you tried Volaris? - Volaris
they fly from Tijuana but if your guests can make the 2 hour drive down from LA to the border sometimes it is worth it. We got a flight for New Years for $275 rountrip. Flights from LAX and San Diego on all the other airlines were $700 plus.
Also they have a shuttle from San Diego that brings you to the Tijuana airport so you don't have to park your car in TJ.