Portland is 5 hours behind Montevideo
Best overlap: 1:00 PM to 6:00 PM in Montevideo is 8:00 AM to 1:00 PM in Portland.
The hours that work for both Montevideo and Portland are 1:00 PM to 6:00 PM (Montevideo) and 8:00 AM to 1:00 PM (Portland). The shared window is roughly 5 hours; treat its midpoint as the default and you'll keep both teams happy. Note the seasonal wrinkle: when Portland is on daylight saving and Montevideo isn't, the gap between them grows or shrinks by an hour.