I don't know about Sylvan, I'll look it up and let you know. I know that Druids are special in that they can learn Sylvan in addition to their starting languages upon character creation. It's the language of the forest creatures and fey.

Edit: Yes you can, as long as your human character has a high enough intellect (but Mana didn't require stats with CSs, so you should be fine). Also, Sylvan pairs well with Elven as both languages are written with the Elven alphabet. Fun facts.

Secondary Edit: Also, I was looking up if there was any way for a non-Druid to speak the language. It looks like (according to the people of the internet, who could simply not know what they are talking about) non-Druids can be taught the language from a Druid or a Blighter (a messed up version of a druid that already lost Druidic powers), but that would involve the Druid losing all of its powers and being exiled, even if the Druid was tricked into it. So... even if you did include that in your character's history, my character would not talk back to you in Druidic for fear of losing his powers, and he would also be suspicious as to how you managed to acquire the language.