Translation:The Italian tourists are where the Polish ones are.
Because English grammar is not like Hungarian grammar :)
In English, where by itself is fine as a relative connector; it doesn't need an additional there.
I'm not sure whether there's a good answer to the question "why" this is so.
mizinamo says it well! Deep logic suggests to me that "there" is, in fact, where "where" is.
It's an adjective modifying turisták. Adjectives don't get pluralized, unless you make them into nouns. E.g., "olasz turisták" ("italian tourists") but "a turisták olaszok" (the tourists are italian).
And "lengyelek" took over for the whole adjective+noun structure. It has the implied "ones", or "tourists", in it. So that's why it is in the plural.
Hm, then that first sentence in this lesson's tips and notes section -
Hungarian differs from English in that adjectives have to be plural when the subject is plural as well.
should have a pretty large asteriks next to it?
Apparently the context was not so clear that that statement pertains to "predicative adjectives", not attributive ones (which, I believe, are also called "adnomials")..
The Tips& notes got modified by now, now it does not say it always have to be plural. Just sometimes :)
I don't hear the 'L' in olasz. It sounds like a 'N' to my ears. It could be my phone but wanted to check to see what others heard and find out if it is a typical pronunciation.