Verified answer

I'm sure they could speak Sindarin, if they wanted to learn, and if there was anyone around who was willing to teach them.

But they have their own language, called Rohirric, and speak Westron, or the Common Tongue, to outsiders.

I don't think they do.

They speak their own langauge, much like every land in the west, even though the Common Tongue is used by everyone at some time or another.

So even if they wanted to communicate with the elves they could just use the Common Tongue.