I think it should be translated, except if the title has some kind of pun, wich wold lose the meaning intended by the author completely - in that case, the title shouldn't be translated and the translator should put a note somewhere explaining the pun.
What I hate the most about translated Titles? I can't look the show/comic/whatchamacallit up because I don't know the original name. You can translate the name somewhere else (underneath it or something) but don't completely cover it. xx
The title of a work is there to define and add value to it. If the title is left in the original language you could argue that you are simply refusing to lower the value by providing an inexact translation, but all you are doing is degrading the work by making it harder for the intended audience to relate to and ultimately fewer people will read/watch/whatever it because they don't feel like it connects to them.
Leaving the original is better! You can make a subtitle in the country's language explaining the title, if that's the case. For example, KareKano here became "KareKano - as razoes dele, as circuntancias dela" and so it goes.
In those cases where the title is only one word, you can keep the english title and put the spanish translation below this title, or you can only leave it alone. But, in cases like "oranges and trees", it would be better to translate it all. Both are good, but it also have something to do with the background (context). In any case, I hope I've helped you as an official and professional translator - since yesterday^^.
Truth is, keeping an English name actually easier and people think it's cool. That's why Japanese shirts and cartoons show clothing with random English words. Apparently, English-speaking people get tracked down in Japan so everyone can practice their English hahaha.