We lived in Boquete for almost a year, and had very few brownout/blackout incidents, even up on the Jaramillo Mountain. However, when we moved to the Boquete Country Club that all changed. At BCC the power went out on a regular basis for some reason, especially during the windy season. We lived on the third floor at BCC, and very soon decided to stop using the elevator for fear that we'd be trapped inside when the power failed. Electricity there dropped off six or seven times a day, for several minutes to an hour. Once it was out for 72 hours. As I said, in the rest of Boquete electric service was pretty reliable, but up the hill, especially at BCC, it was anything but.
Hope that helps.
(House in the mountains near Boquete, Panama, pictured.)