How or where can I edit in-game text?

Depending on your server, (NA, EUW, etc), the file is in a different place. For the current release (3.15) on the NA server, the file you wish to edit is located here:

C:\Riot Games\League of Legends\RADS\projects\lol_game_client_en_us\managedfiles\0.0.0.132\Data\Menu\fontconfig_en_US.txt

In your case, for LAS, search for a file with "fontconfig" in the lol_game_client_es_mx, instead of lol_game_client_en_us directory, and you should be able to find it. The fontconfig_en_us.txt file is all the text in the game. Recommending you open this with NP++, or a similar editor, the four pings are lines 667-700. Changing the words in quotations will change the text ingame.

This modification will not get you banned, for custom skins, custom maps, etc, are not ban worthy, as they do not influence gameplay.