There is no single service that can guarantee coverate, Not even HughesNet (though they come closer than anyone else, but ..Well read on) I use a combination.
NORMALLY I use park Wi-Fi, not always the best and at the bigger parks may be overloaded (long story may tell later, have told before). Too much Wi-Fi junk these days.
But my full "Kit" includes park Wi-Fi, McDonalds, Lowes, Staples, et-al (Public Wi-Fi Nodes offered by stores and libraries) and Virgin Mobile.. I choose VM because I can buy 10, 20 or 50 dollars worth when I need it and no need to buy more next month, This is posted by VM 20 dollar plan.
Hughes has near total coverage (very small and very few dark spots) but is slow and lagged (Being 2-way satellite) which bothers many folks.
If you wish to bring your own all the time, and not rely on public nets (Which does have some risk to it public nets that is) then Verizon has the best cellular internet coverage last I checked, Others are doing their best to change that though. That said I have my own reasons for NOT liking Verizon home of the cuss-some-more non-service department. Been dealing with that dept since before it was Verizon, and still not happy with them. (another long story) .
Home is where I park it!