Would it be a good idea to start defining DCAT metadata terms in other languages, for example, "título" (Spanish) instead of "title" (English)?
I would not recommend translating standard schema terms to other languages. This would make datasets not portable across toolsets that incorporate the schema. Instead, I would suggest mapping the terms to other languages in the visualization (e.g., viewer) of the data.
For example, an spreadsheet view in English might show "title" while in Spanish how "titulo". But the field naming in the raw data would not change.