I personally would never buy before renting in an area.
I believe you need to get "the real feel" of an area before committing long term to it.
An area that you drive through and see a great house in, may not necessarily be an ideal area for you.
You may find that the community feel you were looking for doesnt actually exist, that the traffic to and from the house is worse at times, other than when you have been past.
etc etc.
This is just my opinion...not just for Dubai, but anywhere in the world