If you start from Surabaya, Malang, Jember and its sorroundings, you can start your travel from 12 midnight. Then you will be arrive at about 2 or 3 am. You can rest for a while before continuing your journey to the mountain's top. The food and drink sellers have ussualy stood by in sand-ocean area from that time, in case you need to 'fulfill some fuel' .
Around that time, you may start climbing through the ladder steps that will bring you to the top of Mount Bromo.
Enjoy the sightseeing untill about 9 am, and you can get home again by 12 at noon.
As an addition note, if you di the travelling through the sand-ocean in the middle of the night - as a clue - you had better go to the parking area around The Pura ( Hiduist Praying Temple).
There you can see concrete bollard which purposedly built as sign to The Pura area. And if you lost in the middle of fog, don't be panic because the commercial horsemen will pass the sand-ocean from 2 am.