Translation:Esperantists often travel to foreign countries.
Kaj por fremda (foreign) [Mi ŝatas danki la Google translate-on ĉi tie]
Hispana = extranjero [/redakta]
Rusa = чуж
Portugala = extrangeiro
Korea = 외국
Japana = 外国
Itala = straniero
Greka = ξένος
Franca = étranger
Nederlanda = buitenlands
ĉina = 外部
kaj Norvega = utenlandsk
Batlordy jam nomis la germanan vorton.
As a Spanish speaker, I'd like to remark that "extranjero" would also work. However, when talking about languages, other words can be chosen. For instance: "segunda lengua" (second tongue/language). "Idioma no nativo" (non-native language) sounds a bit too formal to my ears.
"Esperanto speaker" does make more sense in English. But in practice Esperanto speakers are so used to saying "Esperantisto" in Esperanto, that they often mimic the word in other languages. In part out of habit, but also because it's usually a shorter way to say it in most languages. And you usually use the word when talking to Esperantists, anyway.
I guess it's similar to how people who play videogames usually call their fellow players "gamers", even though "videogamer" or even "videogame player" would be more logical and easier to understand to non-gamers. But "gamer" is nice and short, and the people you usually say it to understand exactly what you mean.