Yes, robberies do happen at machete-point, but death by a thousand insect bites is far more likely.
Food and Water
At any given moment in a hostel somewhere in Nicaragua, a conversation is unfurling about whether or not it is safe to eat street food. The answer is yes, or yes in context; it is as safe to eat street food in Nicaragua as it is to eat supermarket or restaurant food. At least with the street food you know who is preparing your food and exactly where they are putting their hands.
With or without street food, be prepared for some interesting intestinal gymnastics in Nicaragua. The basic fare (rice and beans) will plug you right up. The basic hygiene will do the opposite. Whatever your preferred diarrhoea treatment is, have some on hand.
Don’t drink the tap water; there should be bottled stuff everywhere, and where there is no bottled water there is bagged water. These little water baggies are also in large part to blame for the flooding that takes place every time it rains. Since no self-respecting Nica would ever throw one in the garbage, they end up clogging street sewers instead, producing lots of stagnant, brown dengue water.
Blame it on the Mosquitoes
In any places that you’re not at risk of dengue, you’re probably at risk of malaria. Dengue is generally the greater risk; for most of (touristed) Nicaragua you won’t need to be on antimalarials. Either way, make sure you have protection against bugs; even if there were no nasty diseases in the country, there are enough nasty insects around that you’ll still want something with a very high DEET concentration (the stuff with the warnings about how this product can corrode plastics/vinyls/children under 12 etc).
The scrawny street dogs, most of which are very well behaved, are far more likely to give you fleas than rabies. They are also likely to give you their undying loyalty in exchange for the slightest morsel of food or scratch behind the ears. If you don’t get fleas from the street dogs or lice from the street urchins then you’re just not integrating right.
Almost anything (especially treatment for lice) can be bought over the counter at a pharmacy somewhere in Nicaragua. Despite being Catholic to the core, it is pretty easy to find condoms and birth control (again, over the counter). Tampons can be a little harder to find; apparently good chaste girls don’t use them.
Trip Tides and Narcos
The Pacific beaches have bigger surf and stronger currents than those on the east side. The usual cautionary tales of families/foreigners being swept out to sea circulate here too. More likely than being swept away is being dumped unceremoniously on the shore; it gets rough out there, lot of big breaks and submerged rocks. The private hospitals in LeÃ³n stay in business thanks to amateur surfers with travel insurance.
The Caribbean coast, as well as having its share of insect and water-borne nastiness, gets used as a transit point for narcos trafficking between the southern supply and the northern demand. Tales circulate of bales of cocaine washing up on the beaches near Bluefields, but these are more folklore than fact. It may have happened once, but most of the drugs on the coast are headed for far more lucrative markets than any that Nicaragua could sustain.