People are exaggerating the issues with the Viz translation, I'm fluent in both english and japanese, regularly read both raws and english version, and I say it's perfectly serviceable.
First of all I really didn't see any of the flaws
@BuyVelomobiles mentioned in the first chapter, the translation makes it very clear that Ruri is simply an asocial girl who has trouble dealing with being the center of attention, exactly like in the raw, for example. Maybe
@BuyVelomobiles isn't a native english speaker, so they have a hard time reading the subtext in the english version, but the subtext is conveys the meanings of the raw fairly well for me, as a native english speaker.
As for the issue of the usage of slang, it's really not an issue. Mainly because the raw also uses a bit of youngster slang, but also because it's not "gangsta" slang, like how
@Kirin-kun said, but it's very common teenager slang, something that you'd expect a 15 year old kid to say, just like Ruri's classmates. Once again, this might not be obvious for people who aren't native english speakers, but not all slang is "gangsta", the one used in Ruri Dragon is compatible with the high school setting for sure.
TL;DR: The Viz translation is completely fine.