It's only $150. Go ahead and post jury fees yourself. Even if the other side's already requested a jury.
Yes, it's nonrefundable. But, in the scheme of things, it's a pittance.
Otherwise, this might well happen to you too.
Nothing stops the other side -- the side that demanded a jury and posting the fees -- from withdrawing that demand on the first day of trial. If that happens, you've prepped for months for a jury trial, but at the last moment, you have to retool everything for a bench trial. Exhibits, opening statements, etc. Plus, you've already waived your own right to a jury trial by not posting fees, so you no longer have that right.
Sure, you can ask for a discretionary waiver from the trial court. But don't be surprised if, as here, the trial court denies your request. Bench trials are so much easier. Plus, then the trial judge gets to make sure that the case comes out the way s/he wants.
One more thing. If, perchance, the trial court denies your request for a discretionary waiver, file a writ. Do not, under any circumstances, do what the party did here, which was to elect against filing a writ, wait to see if they win at the bench trial anyway, and if they lose, then file an appeal asserting an erroneous denial of your request for a discretionary waiver.
The California Supreme Court holds that, at that point, you've got to affirmatively show prejudice -- i.e., that the result would have been different if the case was resolved by a jury instead of a judge. A showing that is, quite literally, impossible.
So, to reiterate:
Spend the $150.
I'll potentially save you a world of hurt.