Stay healthy:
According to the U.S. State Department's Consular Sheet for Nicaragua, the tap water in Managua is safe to drink- but chlorine is added- bottled water is always the best choice. The water in Esteli is especially good as it comes from deep wells. Bottled water is readily available, 8 to 15 cordobas a litre.
Given its tropical latitude, there are plenty of bugs flying about. Be sure to wear bug repellent containing deet particularly if you head to more remote areas (Isla Ometepe, San Juan river region and the Caribbean Coast.
Dengue Fever is present in some areas and comes from a type of mosquito that flies mostly between dusk and dawn. Malaria is not of serious concern unless you heading to the Caribbean coast or along the Rio San Juan. You may be advised by a doctor to get Hepatitis A and Typhoid vaccinations before heading to Nicaragua.
Contact:
Nicaragua Embassy Washington DC 1627 New Hampshire Avenue NW, Washington, DC 20009 (202) 939-6570
Nicaragua Consulate General Los Angeles 3550 Wilshire Blvd. Los Angeles, CA 90010. (213) 252-1174
The full list of embassies and consulates can be found here.
The application form for a Nicaraguan Visa can be downloaded here.