If you plan to enter medical school in the fall following graduation, you will apply in the summer after your junior year. This reflects a national trend.
Medical schools are in no way biased against later application.
On the contrary, further time, appropriately used, can often enhance an application substantially. This depends on your reasons for waiting. If you have strong credentials and just want some time off, do what you like. If you are trying to improve your credentials, then your choice of activity should be tailored to correct the weakness in your record. Your first criterion is purely geographic.