Mt Nebo-Mt Glorious- and even on to Somerset Dam is a great ride. I would recommend driving to The Gap first, and then departing by bike from there. Plenty of cyclists as well as motorbikes and cars frequent the area. So while common sense is advised. I don't think you'll be anymore unsafe than cycling anywhere else.
Also driving first to Samford. And then cycling to Mt Glorious is also another great ride.
While I grew up in the area, I unfortunately can't advise on alt. off the top of my head. As I haven't lived there for a few years now. We have certainly had some nasty weather, that is now clearing, 2 hrs north of Brissy.
Hope this helps a little, have fun, and safe cycling.