Dear gasg,
1. Do you think it is worth giving my GMAT again? To be realistic I think I can improve my score by 30 points at the maximum. I am planning application for August 2010.
If you can improve your score, I think you should retake the GMAT. While your 690 is in range for your target schools, it is below average. Scoring in the 700s would put you in a much better competitive position, especially if you are applying as an international applicant (needing a student visa).
2. What are my chances for the school that I have mentioned with GMAT score 690 and above mentioned profile?
I think you have a shot at these schools with your current profile. The decision will come down to the strength of your entire application, not just a GMAT, GPA and amount of experience. Do not discount the importance of the essays, recommendations, resume and interview in the admissions decision. I commend you for starting to work on your applications now and determining your strategy--this type of planning and preparation will be worthwhile.
3. Do I stand a better chance of getting accepted considering that I am from healthcare background and will be preferred candidate from diversity point of view of the class?
I'm not sure that you will be a preferred candidate from a diversity point of view. Your educational and professional background is not overly represented, but it is not rare. It is an advantage for you that you are wanting to remain in the health care sector though, as you are not looking to make a significant career change.
Best of luck,
Lisa