Miami is 3 hours ahead of Portland
Best overlap: 8:00 AM to 3:00 PM in Portland is 11:00 AM to 6:00 PM in Miami.
For a call that suits both sides, look at 8:00 AM to 3:00 PM in Portland / 11:00 AM to 6:00 PM in Miami. With 7 hours of daily overlap, these two cities are an easy pairing; almost any reasonable hour works.