Is the language of the mind, English, or whatever your first language is?

Not necessarah-lee, but primarily. It seems that those who know different languages can, with some *effort, switch back and forth.

Are words thoughts?

Yes, but they are not the only *things that are.

Is thinking merely talking to yourself?

I can think a melody. I can think in multiple part harmony... so the answer is: No, but it does seem to be self-oriented.

Is communication a way to transfer thoughts from one mind to another?

That, IMHO, depends on your intent.

Can you speak as fast as you think?

For me *they are about the same speed.

Are sounds or colors thoughts?

The above consensus says: Yes.

Are some thoughts unspeakable or simply ineffable?

I say: Without a doubt!