Welcome Jenn, from another Ontarian.
I admit I was lucky when I first started using a gym, it was one where I was working at the time. Everyone was friendly about it, and very supportive. I've even used the one at Mohawk (I'm back in college) a few times, and maybe there are looks, but I likely avoided them. It really is a shame that people can't be impressed that you're there in the first place. Shame on them.
Anyway, have a look around the site and you'll likely find a few areas that interest you. The two I can think of off the top of my head are:
The 300+ Club -
http://www.3fatchicks.com/forum/forumdisplay.php?f=124
Crazy Canucks Cluck Club -
http://www.3fatchicks.com/forum/show...=167271&page=4
You'll find other groups based on age, or type of plan they're following, etc.