Translation:Es una buena banda.
Why does "buena" come before the noun in this case? Would "Es una banda buena" work as well?
Pretty much, I'd say. Bueno/buena is very often, it seems usually, seen preceding the noun. Some grammar books say that putting the adj first means that you are emphasizing an intrinsic quality of the noun, like "fiero leon" = ferocious lion. I've never made much sense of it, however.
In a thick grammar I read, it has trouble explaining the nuances of the adjective-noun order, and says that in many cases the difference may be so subtle that it is untranslateable in English. However it did also give a good list of adjectives that tend to take on a different meaning depending on whether they're preposed or postposed. Por ejemplo:
Ella es una chica rara = "She's a rare chick"
Ella es una rara chica = "She's a weird chick"
Or something like that.