Caribbean Nicaragua is a region in Nicaragua.
The Caribbean coast of Nicaragua is truly one-of-a-kind. Once a haven for pirates and contra rebels, it is on the furthest edge of Nicaragua's Autonomous Regions. There are six distinct ethnicities and five languages that make up this cultural rondon.
The climate of this part of the country is notable insofar as it doesn't have a real "dry" season and Bluefields, for example, averages 225 rainy days a year. Although a day with nothing but rain is uncommon, your best bet for a relatively dry experience would be March and April, which could be labelled the "drier" season.
Hurricanes do affect this region from time to time, so if you are concerned, avoid hurricane season (roughly June to December), which is one of the wetter parts of the year, in any case.
There are some rural places on the Caribbean coast where people might not speak Spanish. Common languages along the Caribbean side of Nicaragua are, in ascending order of speakers: Rama, Garifuna Miskito and Caribbean Creole English. Because Caribbean English can be hard to understand (almost impossible to decipher for most of those for whom English is a secondary language), Spanish might still be your best bet. More developed places (notably the Corn Islands) often have a lot of recent immigrants from Spanish speaking parts of the country, especially in tourism-related jobs.
Transport is mostly by boat or on awful roads. Most domestic flights go into and out of this part of the country. The road from El Rama to Managua however is one of the best in the country and there's a new (2019) road from Nueva Guinea to Bluefields.
Depending on where you are food ranges from very basic Nicaraguan fare to truly mouth-watering seafood and coconut-extravaganza. Every meal usually includes Gallopinto, which is rice with red beans. A special treat is ron don (from English run down) a fish and coconut stew that takes time and expertise to prepare so order well in advance. Especially in the RAAN-region but also around Pearl Lagoon there are some indigenous communities who keep their culture, their food and their language very much alive. Although this often requires planning ahead and time and effort to get there, experiencing their cuisine as well as their culture could be well worth it.
This part of the country is not unaffected by drug traffic so crime is more common than on the Pacific side. However, with a basic level of caution you should be safe.