I'd mix a bunch of these answers, A friend is writing a story with a conlang in, and the characters code-switch a lot, so instead of saying 'switched o conlang' everytime she just writes in the conlang. Sometimes some sort of translation is given in different ways, sometimes it is not. There are a lot of conlang words mixed with the dialog and I believe that gives a very realistic feeling of how people would code switch in real life in a similar context. It all depends on many things. Does the POV know the language? is it theirfirst or second language? how fluent are they? and also, and more importantly, what do you want your audience to know. So I wrote a story with several conlangs in, and words in them are thrwn arround wquite frecuently, for different effect. One is to differentiate the cultures a bit more. The other one is to give a sense of 'alien' culture, since this words aren't translated, there is probablynot a word in english to describe the thing quite well so it seems foreign to us. Like the lider's of one of the cultures are called Sivos and you're not supposed to know the meaning of the word, just that it's a title leaders get. Or one character talks about the tiizo games or tge Vannbaali and the vanntal. It also helps with names, by giving each language a different orthography and just a different feel all together you can create names that look quite distinct one to another. Kinda like in got you know Viserys and Daenerys are from a different culture than Drogo and Raqqaro, and them from a different culture than Eddard and Ramsey. The orthography and the feel just help further the divide and create a more real and grandious world. Also you can teach some of the words to the audience and use them in clever ways at the end. I can only come up righ now with a character teachen some words in conlang to non conlang friend, and when non-conlang-friend finds themselves in a dire situation with conlang-people, they can use those words to earn trust, and stuff like that. Or that with names, Specially if the conlang-people use viking like compound names. If you know a word means something you can use that to make the audience draw conclutions about a character based solely on their names. You'd have to see how the conlang adds to the story and use it to the best advantage.

I'd mix a bunch of these answers, A friend is writing a story with a conlang in, and the characters code-switch a lot, so instead of saying 'switched to conlang' every time she just writes in the conlang. Sometimes some sort of translation is given in different ways, sometimes it is not. There are a lot of conlang words mixed with the dialog and I believe that gives a very realistic feeling of how people would code switch in real life in a similar context. 

It all depends on many things. Does the POV know the language? is it their first or second language? how fluent are they? and also, and more importantly, what do you want your audience to know. 

So I wrote a story with several conlangs in, and words in them are thrown around quite frequently, for different effect. One is to differentiate the cultures a bit more. The other one is to give a sense of 'alien' culture, since this words aren't translated, there is probably not a word in english to describe the thing quite well so it seems foreign to us. Like the leaders of one of the cultures are called Sivos and you're not supposed to know the meaning of the word, just that it's a title leaders get. Or one character talks about the tiizo games or the Vannbaali and the vanntal. It also helps with names, by giving each language a different orthography and just a different feel all together you can create names that look quite distinct one to another. Kinda like in got you know Viserys and Daenerys are from a different culture than Drogo and Raqqaro, and them from a different culture than Eddard and Ramsey. The orthography and the feel just help further the divide and create a more real and grandious world.

Also you can teach some of the words to the audience and use them in clever ways at the end. I can only come up right now with a character teaching some words in conlang to non conlang friend, and when non-conlang-friend finds themselves in a dire situation with conlang-people, they can use those words to earn trust, and stuff like that. Or that with names, specially if the conlang-people use Viking-like compound names. If you know a word means something you can use that to make the audience draw conclusions about a character based solely on their names.

You'd have to see how the conlang adds to the story and use it to the best advantage.