Here's some examples of what im trying to translate if you or anyone else could help:
stuff
The good news about pretty much all of that is that the English versions will fit within the existing character limit. Now to translations. Please note that much of these are not literal translations and are a close as possible to what is found in the English games (which what I presume you want). (For example: Oir doesn't mean Sound. It means "to hear" but that looks silly in context)
Bag:
Objetos = Items, Volver a = Return to, Cerrarla = Close
Battle:
quiere una batalla = wants to battle, ¿Qué hará RIOLU? = What will Riolu do? (This one is longer in English), Luchar = Fight, Mochila = Bag, Huir = Run
Clock:
Está correcta la hora = Is this the right time? Si = Yes, No = No
Options:
Empezar = Start, Opción = Options
Start Menu:
Maleta = Bag (I think it's interesting that they used a different word for bag in the menu and in battle) Guardar = Save, Opciones = Options, Salir = Exit
Start Menu Options:
Velocidad = Text Speed (longer in English), Len, Med, Rap = Slo, Mid, Fas
Escena Bat. = Battle Scene (could just be shortened to scene to save space)
Estilo Bat. = Battle Style (same as Battle Scene) Oir = Sound (options Mono and Stereo remaining the same) Modo de L/R = L/R Settings (I think English FireRed just has it as LR without another word? I don't remember but you might have to do that because of space issues)
Barra = Frame, Irse = Exit
Hopefully this helped!
If you have any other translation needs feel free to VM me (might be easier than on here). I've been speaking Spanish for 14/19 years of my life so I know a thing or two. :D