A Spanish Spanish speaker (one from Spain) would never, ever say "nunca jamas." Such a double negative would be unnecessarily reiterative. They'd - depending on mood, context, color coordination - choose between either "nunca" or "jamas".

Also devuelta, which is interpreted "as a turn" or "again", California spanish is awesome, espcially CALo a very "ghetto" form of Spanish.

It could really be spelled "de vuelta" literally (From Turn), it means again.

Calo is a creation of a miture of English and Spanish that has evolved over the last hundred years, It's mostly used in Prison Society as I understand it.

Not to say that "devuelta" is not reallly used in Mexico City. I heard devuelta used all the time in Provincial Mexico all the time; as oposed to otra vez, (another Look)
de nuveo, (of new)
or,
una vez más (one look more) as literal interpretations.

Spansh is influenced by the Arab world and Hamas or Jamas sound like one of those funny things the spansih created to say never to Hamas! - or never to the Moroccans and the Arabs.

I agree that (Spain) spanish grammar is very precise, but that is why I added a side note saying "hasn't anyone ever heard in spain:
"subir arriba", or "bajar abajo"... it is a butchery of spanish grammar, BUT it is ok with me =)
In my opinion, the main difference between spanish from spain and spanish from latin-american is the ability that spaniards have to bend grammatical rules in order to bring a personalized expression by using the language as a metaphor . That is why I must say that even though "nunca jamas" is a double negative, it should be ok depending on what one is trying to express.
"Nunca Jamas" might be rarely said in Spain, but at least there is always something like "Entrar adentro"
=)
gabriel