I agree with Dhavaer on the Wisdom. When I converted the Andalites to D&D I only gave them a +2 Wisdom and I'm beginning to wonder if I shouldn't get rid of it all together. After all, if you'll recall from The Ellimist, most of their technical advances were prompted, if not given to them straightfoward, by the Ellimist. My intelligence bonus is about equal to what yours is, so I wouldn't bother changing it; however, in my oppinion, it's more of a "Social bonus" than a Racial one (that is to say, I think an Andalite who didn't grew up in their society would have the Intelligence bonus).
I had expanded on the thoughtspeech ability and limited its use a bit to counteract "Silent" spell casting. It doesn't matter if you don't think it will be a problem for you.
I definitely think that the Natural Armor bonus should be lower. Looking at the MM (pg 298), a +4 should be roughly the equivalence of a Crocodile (tough hide). I figured that, being closer to deer than horse (as you noticed) they should have a slightly less durable hide. Thus, a +2 on my adaptation.
All in all, it's cool to see others around that liked the series enough to make D&D creatures from it.