There are lots of group rides originating in the GTA, it can be tricky to find groups and rides that are friendly to novices.
I wouldn't be scared about joining a group ride -- but keep your eyes wide open and understand the risks and how to manage them.
In a group, or when riding with a buddy, you manage your relationship between risk and skill, .groups and riding buddies won't normally do that for you. I've seen countless developing riders get caught up in the speed of a group, overreach their skills, and crash. Just because a ride is "open to everyone", don't assume that's a good ride for you, many of these rides start tame, but when riders warm up and hit twisty uncongested roads things can get wild.
Don't expect instructional help -- you might get lucky and get good advice or feedback from a capable rider -- you're just as likely to get poor advice and feedback. Ditto on learning by observing -- the chances of learning bad habits are about the same as learning good ones.
If you're on a group ride and it gets too fast or too technical, no shame in dropping out and heading home at your pace.
I always suggest new riders read and watch the videos in 'A Twist of the Wrist' by Keith Cole. I think the book is $20 bucks, it used to include a CD with videos, probably on YouTube now. You can practice as you make your way through the book.