I had a thought the other day that I really love hanging out with other Spanish-English translators. We don't have two languages in which we communicate; we have three. People think that Spanglish is for amateurs, but I tell you that it is for the pros.
I can't think of any examples right now in English, but there are some things in every language that just are awkward to say; however, since we don't know any better--we don't know they are awkward--we just keep saying them. There are also things that we used to say in English which were more efficient but now we don't say them that way because the word has become antiquated. In Spanish, it's easy to give an example off my head:
My father's mother's mother's father's mother was Native American.
La mama del papa de la mama de la mama de mi papa era indigena de los EE.UU. ("The mother of the father of the mother of the mother of my father was indigenous of the U.S.") All of those "of the" is just ridiculously complicated if you ask me.
Then there are words that exist in English that don't exist in Spanish such as siblings and grandparents. Sure, you could say "hermanos" for "siblings," but it could also mean just "brothers." The same goes for "abuelos" which could mean either "grandparents" or "grandfathers" (most people have 2).
I guess the best examples I can think of in English off the top of my head have to do with verbs. In English, you need to have a pronoun (or name) in front of a verb to explain who the subject is. In Spanish, because the verbs are constantly changing--probably the hardest part of Spanish to learn--you usually don't need to explain who/what the subject is because it's included in the verb.
I want to sleep. You could say "Yo (I) quiero dormir," but it's completely unnecessary.
Necesitas lavar los trastos.
You need to wash/do the dishes.
So, when we speak Spanglish, we can come out with this:
"Tengo que lavar los trastos y la ropa, pero les encontrare at John's house at 3." instead of
"I have to wash the dishes and the clothes, but I will meet you all at John's house at 3." or
"Tengo que lavar los trastos y la ropa, pero les encontrare en la casa de John a las 3."
Some of us fall in and out of languages easier than others. I'm not sure I'm bilingual at this point. I think I just have one language with a very large vocabulary and two sets of grammar rules. Just as when you use English and modify your vocabulary based on your audience, I do the same thing. However, it's not so much based on how advanced the words are as it is the "type" ("language") of vocabulary.
Just some idea that has been floating around in my head for a couple of weeks...