A will usually does not say how or where you want to be buried/cremated.

Yea,but usually if u want your wishes known for burial...then usually u have a will

Those are two different things. Both my father and mother made a will. My father told us he wanted to be buried in his home town. So we did that. My mother never talked about it and her death was pretty sudden, so it was up to me to decide where she was going to be buried. I'm pretty sure you can include wishes like that in your will if you want to and I only have my own experiences to go on so I can't really answer your question, but I think in Prince's case, it was the family who decided.
[Edited 4/28/16 7:05am]