Who's subtitling Go-Buster?
 

Over-Time was my usual source for shows but they're apparently still undecided (and since they haven't even put up a raw that's probably a sign they will not handle the new series).

What other groups can/will handle this new Sentai?

TV-Nihon will almost certainly do it, and I think Grown Ups in Spandex expressed interest if they can get a weekly timer to do it.

Other than that I've no idea.

On JEFusion they are saying that Over-Time is working on the script for Go-Buster

They posted an image of the script file up on /m/ too (I saw it on JEFusion's Facebook page) so I guess we'll find out soon enough.

I typically default to TVN but I think I'm gonna be going with Over-Time for Gobuster. I'd like to at least keep up with everyone else watching the series. I'd like to not wait the extra 4 days for Nihon this time around like I did with Gokaiger.

Always stick with TV-Nihon, I've relied on then since Dekaranger in 2004 they've always been on point. I wouldn't worry about the other guys.

Probably the same people who subbed Gokaiger. I would see no reason for them not to.

As for GUIS, I'm not sure I'm going to trust them again, as it seemed they just dropped Gokaiger at episode 28, so I went with Nihon afterwards, which was very annoying. I hate switching fansub groups in the middle of a series, as it throws everything off. Anyway, Nihon is who I am going to stick with. They might take longer, but at least they release the entire series and the files work on my BD player.

A lot of that was outside of GUIS's control, in fairness. There website went down for a couple of weeks during Gokaiger and they've mentioned having trouble keeping a regular timer for their subs.

Time to try them out, then.