I vote Nov-Dec. People usually had 5-6 interview in both months. Most students for medicine in my school had 2-3 in Oct and 2-3 in January. You can pick the earliest date possible. I knew that I wouldn't want to travel in January after having a holiday period, so I only scheduled one in January.
Even after you pick an interview, you can contact the coordinator or see if there are any other dates on the scheduling website.
Additionally, although rotation coordinators have a cow over students missing dates, most attendings are fine with you missing reasonable number of days in clinic. Note this means 1.5 days at most, unless flight delay, etc. They know you need to interview. If it's hospital months, you might need to go in over the weekends.
