In HBC I think they say that Visser 3 was studying up on Andalites before he had a host so they probably have some way of learning, maybe school or a computer they can access in their natural state or something.
As for me, if I were a Yeerk grub, well that's easy. I already know that had I been a Yeerk they wouldn't have lost the war, and I'd be emperor right now, as a grub I'd have been extremely busy learning everything about humans, especially military tactics (learn about your enemy and all) just as Visser Three had learned all about Andalites, with all this human study I'd have been interested in the peace movement but would never have accepted noninfestation, it's too detremental to my grander scheme you see, so while I would do nothing to hinder them (providing they in turn did nothing to hinder me) I would not join them.
As for the Andalite Bandits, I'd hate them of course, this is from a Yeerk's perspective after all, and even Aftran the friendly Yeerk hated Andalites at first, I'd need some sort of major event to change that, just like she did. Infesting my eventual Andalite host (bwahaha) might eventually lead to some understanding, but alas by then I'd be all grown up, and I've already discussed what I'd do as an adult Yeerk
