"It is an old hotel."
Translation:Ez régi szálloda.
No, you can't. You will usually use the "van" when talking about the location of something. That is the most common case.
"Ez a szálloda itt van" - This hotel is here.
Or when there is an adverb at play, not an adjective:
"Ez a szálloda zárva van" - This hotel is closed.
But when you have an adjective, there should be no "van":
"Ez a szálloda régi." - This hotel is old.
To reply to my own question, it's incorrect because the adjective should come before the noun in Hungarian. So even if I made it grammatically correct Hungarian by adding an article to make eg "Ez a szálloda régi" (as Krzysztof672877 explains above), that would still mean something different: "This hotel is old" rather than "This is an old hotel".