Brazil was (really) very expensive, possibly higher than Boston. So, don't recommend it as a cheap away location unless you have a good lodging option. If you can find good internet, Managua in Nicaragua is a fun city with lots of beaches, volcanoes, and old cities to explore on the weekends.
If you want something logistically easy, the Yucatan in Mexico has tons of options and is relatively cheap. Tulum is not too crowded, lodges have good internet in the commons areas.