Translation:Have a nice trip!
The only problem word for the masses would be "en masse" (seriously, even though it's a nice POW - Play On Words).
"Soup du jour" is very common. "Au jus" also, bastardized now to "jus". "a la mode" is extremely well known (here it means "with a scoop of [flavor] ice cream".
It depends on the level of education. Even without knowledge of French language, there are many imports into English which now serve as "English" words. It happens a lot, and from many languages.
That's one of the reasons English is so hard to spell "correctly" and to pronounce simply by looking at the word's letters.
As an aside, one of my favorite phrases is "English is the lingua franca of the world". Idiomatically, "English is the international language". Literally, "English is the Latin phrase meaning the French language" or "English is the French of the word as expressed in Latin."
When it comes before the noun, it has a more subjective meaning (nice) or it adds intensity (really good). When it comes after, it's more objective (good vs bad).
It's easier to see the difference with a word like "grande". Before the noun, it means "great" or "fine"; after the noun it means "big".
Section 4 "Meaning-changing adjectives" here http://www.spanishdict.com/answers/100027/adjective-placement#.VWRc1VJ27vg has a list of this kind of adjective with the before/after meanings. (For bueno, they list "good" in both columns ... :-)
I think that 'Bon Voyage' is used in most of the English speaking countries (as Daniel-in-BC mentioned). As well as borrowing phrases from other languages, we like to be concise and the French 'Bon Voyage' rolls from the tongue more smoothly than, 'Have a good trip!' but another feature of the English language is that we have so many ways of expressing what we mean. It is a rich language and I believe that as we become more fluent in Spanish, we will discover that there are also many ways of conveying a thought and understand the nuances implied in each of them.
I was unable to reply to your comment below, so I must do so here.
Not only in English, but all across Europe in fact, French was considered the aristocratic and sophisticated language in the past. This became so much the case in Russia, that the royalty and ruling class began to speak French so well that they forgot how to speak proper Russian! It is still very much the case that using some French in one's everyday speaking is seen as desirable and sophisticated in certain academic and social circles in England. Latin also possesses this trait.
I'm not sure what you mean ... It is a very common expression in English, to the point where it is the most natural way of expressing the idea for many native English speakers. English borrows and steals a lot from other languages; all languages do to some extent. In this case, we stole a whole phrase. (deja vu and bon appetit are other examples from French)
I was pointing out something mostly about Louisiana culture, being that we have a lot of cajuns here and are immersed in French more than a lot of states in the US. So because I automatically distinguish that it is a French phrase, it shows that much more that I am a Louisiana gal. Language connoisseurs can see the difference and actually note that it is French, but even if I weren't interested in languages, I would still see it because of my heritage here. But I was saying it's interesting to me that it's such a commonly accepted phrase to English speakers and considered as an English translation.
The English language grabs words and phases from other languages when there is not an easy way to say the same thing and thus it becomes a part of the English language such as cul-de -sac and chauffeur. And even connoisseur is French in origin.
I believe Delicatessen, Hamburger, Frankfurter are just a couple of words adopted from German into the English language.
I don't think your comment was taken as an insult and I find it quite interesting to learn about practices common to states, provinces or regions which have differing heritage mixes than the 'average', if there is such a thing. My own British mother and grandmother had quite a sprinkling of French phrases and they both, as well as my great-grandmother had French given names. I got the impression, although I don't know if it was correct, that some classes or groups tended to use these phrases in order to sound 'upper class'. Could this have been a trait which is as old as the Norman conquest of Britain, when the ruling classes and nobility spoke French?
As a Hiberno-English speaker, not that I personally use this phrase, but as it is an incredibly common way to say "bon voyage" in Hiberno-English, I do think that it should be accepted.
Your point about a perceived element or risk reminds me of one of the funny subtitles between Hiberno- and British-English. In Hiberno-English to say "good luck" in all variety of situations, such as in place of "goodbye" for example", is extremely common, however British-English speakers are usually a little confused by the expression, as you seem to have been, often responding "good luck with what?!" !
Not quite an English 'h' sound, although for people who have difficulty in pronouncing the Spanish 'j', it is quite close. I always describe the sound as that of the 'ch' at the end of the Scottish 'loch', always providing that you don't pronounce it as 'lock' of course!
Because the intention is to translate the Spanish into a phrase which is used by English speaking people. 'good travel' is not something you are likely to hear and if you said it to an English speaking person although they might figure out what you meant they would know right away that you weren't familiar with the language. Literal translations from one language to another sound awkward and here we have the opportunity to learn the right way to converse with others. :-) I have similar mistakes when trying to write or speak Spanish, but with practice I am trying to get better. Buena suerte!
When you wish someone a good trip or 'bon voyage', you are often wishing them an enjoyable trip. Of course, you might also be hoping that it will be a safe trip but it is not really quite the same. I often check things and their meanings at www.Spanishdict.com. Their offered translation for 'have a GOOD trip' is que tengo buen viaje but the translation for 'have a SAFE trip' is ten un viaje seguro. --So not really the same in English or Spanish.
The reason is that Bon Voyage!, even though in then French language is used as an English idiom. England was invaded over the centuries by many cultures and so the English language has many borrowed phrases. This particular question is using a Spanish idiom and looking for an English idiom in return, or the reverse. The literal translation doesn't actually matter here and I don't know what your own native language is but I am quite sure that 'nice travel' is not something called out to a person going on a trip. Please let me know if this is used in your part of the world and I will stand corrected. :)
Have you ever told anyone "Good travels"? I never have. It's always "Have a good/nice trip" or, very rarely, "Bon voyage".
"Happy trails" was an expression that was used mostly in American Western movies/TV programs that was popularized by Roy Rogers, but it is rarely used outside of such a context.