Puerto Rico is still recovering from Hurricane Maria several months later, but it should have the benefit of thoroughly modern networks as it returns to health. T-Mobile now plans to roll out its 600MHz Extended Range LTE networking in the US territory this fall. This should provide more coverage and capacity than you sometimes see on the mainland (it has twice the range of "mid-band" LTE, T-Mobile claimed) as long as you have a compatible device.
Source: T-Mobile
