GMAT Strategy

I need some advice,would be glad if somebody can help me out.

My gmat is on the 16 th of September.

I have to apply for fall 2010(cant delay it any further), But my mock scores are in the 550- 590 range.

I would like to apply to one of the decent schools in the US if not the top ones ( atleast schools ranked in the 25- 35 range)..

DO u suggest that I postpone my date ?
Or its possible to reach 650 levels with the time I have in hand?

Awaiting your reply,