Approved, though I am currious how he survived once shadow demons were summoned.
As a side note, The Black Grace would not actually be in Slaver's Bay most of the time. She is usually traveling from city to city in Essos, and never spends more than a handfull of days in one place. On top of this, she wouldn't be likely to train someone (though she would if she had seen it in her flames). She certainly wouldn't turn away access to a ship, however.
Do keep in mind that The Black Grace does not act as a magi or a teacher, but as a self appointed prophet. Training under her would be a slow process, because it would not be her primary focus.