I don't know what OP did, but I have a colleague who must commute daily from San Bernadino to the Venice/Marina del Rey area, and I can state with some confidence that United Express flies at least a few flights daily between LAX and ONT, mostly Brasilia 120s although I think they mix in an occasional CRJ.
Upon review, however, doesn't look like flying would meet OP's a) budget or b) time constraints! Eek!