I have joined an institute for CAT 2011, have just started my preparation seriously from today, is it too late to start from mid june?

depends on earlier capablity of anayltical power, english and efforts this year and the particiapation in group discussions. it is never late, even if u dont succed this year than also you will be able to analyse urself --ur performance will be indirect indication the line u should proceed.

No, its not too late, you have approx. 6 months. you just have to do your study with complete dedication.