For Pokemon Games, the program used to edit the text is thenewpoketext: *Click Here To Download*
Thenewpoketext so far has been able to edit (As far as I Know of) Pokemon Diamond, Pearl, Platinum, Heartgold, and SoulSilver.
For other games, it is a variety since every game for DS is made differently. For other games, usually someone or yourself have to come up with a tool to change the text. Hope I helped.
it is kinda funny because I don't even speak spanish but I joke about this with my friends all the time, it seems like a lot of people in spanish-speaking countries uses the word "buseta" to refer to bus