For Nicaragua I suggest staying in Managua as your base (the Hilton is really good) and then renting a car to drive to the nearby sights in Granada, Masaya and Leon. I did this two years ago and had a great time, it's a beautiful country.
I disagree with the above advice.
Managua is a big, sprawling, mostly ugly city with, admittedly, some great hotels and restaurants. It will also be your best bet for reliable Wi-Fi too. But Granada and Leon excel in their selection of colonial architecture that has been converted into charming inns -- good Wi-Fi is pretty standard in those places too -- and trendy restaurants and in sights in general too. I think it would be a shame to have to rush back to Managua each night.