You really dont even need to be in a large cosplay group, just have friends around you at all times until you're more comfortable walking around on your own.
When I first started, I had my friend Joseph stick to me like glue because I was so nervous and afraid that someone would try to beat me up. It took a little while, but now I walk around all by myself and I've found that it's not as bad as I thought it was originally. Sure some people can be mean, but ever since I started crossplaying in 1999, I've had only like 3 instances of jerks bothering me. And they were 'hit and runs' most of the time, or just brain farts where the person speaking wasn't really thinkign. Hit and runs are where the people aren't brave enough to say anything to your face, and will pass by and say something obviously loud enough for you to hear and keep walking.
What I get the most of are people complimenting my costumes and bravery. Some even come up to compliment my costume, and are startled when I say thank you, then they're really impressed ^^
So give it a try, but keep friends around you for a while, until you're ready to fly on your own. ^^