What language do they speak in El Salvador?

I have worked with people who don't speak English, The ones who have come from El Salvador, have had to learn both Spanish and English, the spanish only speaking people have had to ask others to translate for them. I have heard one guy in numerous conversations on the phone with family, It sounds to me like a creole mixture with Japanese, or something
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For the people who think that I'm an idiot that I don't know they speak spanish. I do know that Many people from El Salvador speak spanish. I know some that do not speak enough spanish to communicate with other spanish speakers, such as people from Mexico, Cuba, Dominican..... They came here and they had to learn spanish and english.