What is the best medical school for the specialization of cardiology?

Johns Hopkins University School of Medicine

A med school doesn't train you in a medical specialty.  The first two years of med school gives you the basic sciences needed to understand how the body functions.  The second two years exposes you to patients in the major specialaties within medicine to give you a solid foundation in treating all sorts of patients.  After you complete the four years of med school you decide which medical specialty interests you the most and then you apply to residency programs that offer that specific training.  In your case, Cardiology is a subspecialty of Internal Medicine.  You will do a residency in IM and then follow that with another year of two of specialized training.  

Where you go to med school isn't as important as where you do your residency.  Since you have to pay for med school, I recommend applying to the state university within your own state (it will be the least expensiove option for you).  When you are ready to apply for residency, then you can consider programs outside of your state (because you get paid during residency training!!)