I think it would be possible for us to have the ability to learn dwarven, due to there being a few dwarves in the area. What I think I am going to do for Owen is leave those blank and kind of have him learn languages along the way. For example, while adventuring we have to camp for a night. Before going to bed, Owen tries to strike up a conversation with Gregor, Azten or Kenneth in their native tongues (eventually learning the language). Maybe Owen will pick up a translation book or something during his adventures. But I think for right now he is only going to know Common (and have 3 slots to fill along the way).
Any of those native to the basic PC races are possible. While there aren't a lot of dwarves, elves, gnomes, etc., in Diamond Lake, it is still possible that Alexi would have some exposure.
More obscure languages may also be possible, but we might have to get creative to explain how she knows them.
Sorry it's been relatively quiet these last few days. I've been making preparations with my family to head out of town for a little vacation. We'll be leaving today, and returning Thursday night. I may have some brief Internet access, but I probably won't be able to post anything substantive until Friday. We'll get back into the swing of things when I get back.