Can you teleport outside? Sure.
Is it safe? So long as there's no rain to smudge your diagram it's basically as safe as doing it indoors. And in Lucien's defense there wasn't any rain at all, right up until the last sylabble of the incantation.
"Terminal patients who agreed to donate their bodies to science in return for money for their families. I don't feel good about it but I think it was the right call each time."
"Sounds like the way to do it if you're gonna, certainly. - I should bring in some Elves, reduce the risk that I lose my door."
"Yes. I trust her and she might be both near the door and a person. I'm not sure."
"Well, I'm not sure a cat could open the door if you couldn't but I like cats if you want to bring her in." He pulls open the door. "Alassëo, come here."
Lucien can have a go.
"Fi-" he doesn't actually finish saying her name before a furry brown cat darts into the bar. "-ka. Ah, there you are."
Fika looks up at the demon briefly, before deciding that there's more interesting things to investigate at the moment. Such as this Bar that she has just climbed onto.
... This presumably means the bar is safe to drink from. He'll order an iced tea while he waits for the demon to finish catching the elf up.
The thing is Lucien didn't actually bring Fika with him to the flat in Istanbul his door opened up to. And yet.