Learn Spanish (Latin America): Preferiría que ustedes guardaran esos fondos. - I would prefer that you guys keep those funds.

The main verb preferiría is in the conditional tense (would prefer). When the main verb expressing a wish, preference, or request is in the conditional or a past tense, the verb in the dependent clause (after que) must be in the imperfect subjunctive. So, preferiría que requires guardaran, not guarden.

Since preferiría doesn't have an explicit subject like yo, could it also mean he or she would prefer?

Yes! The conditional forms for yo, él, ella, and usted are identical. Out of context, preferiría could mean I, he, she, or you (formal) would prefer. The English translation tells us it means I here, but in a real conversation, you would add yo if it wasn't already clear.

Could we drop ustedes and just say que guardaran esos fondos?

Yes, you can. However, because the -ran ending of guardaran can also apply to ellos or ellas (they), including ustedes makes it crystal clear who you are talking to. It also adds a bit of emphasis, like saying I would prefer that you guys keep them.

I thought guardar meant to put away or to save. Why does it mean to keep here?