"Taking photo is forbidden."

Translation: Dilarang mengambil foto.

[Ria___]

Is "memoto" a standard Indonesian alternative to "mengambil foto" or is it too slang/informal?

[Rick392366]

No, that's not standard.
You can use a synonym, like this :

"potret" (noun) = foto, picture.
"memotret" (transitive verb) = to take a picture.

https://kbbi.web.id/potret

[Ria___]

Okay, that's good to know. Wasn't sure whether it was widely used or just local slang influence. I assume it's shortened from "memfoto" as slang?

Googling "memoto" to find more info, I happened across a camera company called Memoto that says something very interesting (albeit irrelevant...):

And a fun fact about Memoto is that it was not until we launched a Kickstarter campaign that someone told us on Twitter that "memoto" actually means taking photos in Indonesia, and they said it as matter of fact, like, "It's so cool that they chose an Indonesian name for the company," and we were like, "What do you mean?" It means taking pictures and it's the most common slang term for taking photos in Indonesian.