I would recommend IN FAVOUR of trying to play both hands together on the first time that you try the piece.
But I would recommend AGAINST disregarding rhythm. If you have long notes and short notes, make them last for a long time and a short time respectively, and so on. Otherwise you will be in danger of making a complete nonsense of the piece.
However, unless you are a sight-reading genius, you will probably not want to play it, in your very first attempt, at high speed, even if that is called for by a written direction or by a Metronome Mark. Something a little more cautious and comfortable will allow you to get the basic details properly in proportion to each other. What you will want to do on the first attempt is to hear and follow the Melody of the music, and understand how it moves on to become something else, and then finally returns to its home.
Yes, by all means practice afterwards with hands separately. But ALWAYS be sure to work out the exact rhythm of the notes and try to play this correctly from the outset. It is as important as the position of the notes on the keyboard.
Good luck !