El Salvador is the only country in Central America that has only a Pacific Coast. To its east, Belize similarly has only a Caribbean coast.
El Salvador
The only country in Central America that does not border the Caribbean Sea is El Salvador. All other Central American countries do border it.
San Salvador is the capital of El Salvador, the only country in Central America that does not border the Caribbean Sea.
The Pacific Ocean and Caribbean sea
El Salvador
Costa Rica is not an island, it is a country.
Latin America is a cultural region spanning Mexico, Central America, South America and the Caribbean. If you have to define a border, that would be the US-Mexico border.
No country in North America has only a border with the Pacific Ocean. There are several in the Caribbean that are in the Atlantic, but none with only the Pacific.
The Caribbean sea
No the Caribbean Islands are not part of South America. It is actually a set of Islands off the coast of South America and is not really considered a continent.
Of the seven countries of Central America, 6 border the Caribbean Sea: Belize, Guatemala, Nicaragua, Honduras, Costa Rica, and Panama. All Central American countries but El Salvador border the Caribbean Sea. All countries but Belize border the Pacific.
Belize
Belize is the only English-speaking country in Central America. It borders Mexico on the north and the Caribbean on the East. It also shares a border on the west and south with Guatemala.