Talking to imaginary friends? Never. But I do talk to people I know in my head.
I don't have long, full conversations. But I think about what I could say in future conversations. Sometimes out loud, sometimes I don't.
Talking to myself about random stuff? Yes, very often.
Although, when I talk to myself (usually in my head, but sometimes very loud), it's a bunch of random things: quotes from a movie or commercial, swearing, things to stay positive like "come on, you can this", or "ahh, that wasn't so bad".
And I almost always do it in English for some reason, while I actually live in Belgium. Still don't know the reason behind it, it just happens.