When/if I get Facebook...?

[Tennis]

I'm thinking of getting Facebook, but the problem is I don't know ANY girls my age at all other than family cos i go to an all boys school and i'm a little shy and awkward when i first meet people. I know I will be judged if I get it and have no female friends.
Will girls who I knew 3 years ago at primary school add me when they see I'm friends with other guys from our primary school? Or will they just think I never spoke to him even at school, no point adding him?
I NEED to know what most people esp. Teenage girls do when they see someone on Facebook they know the name of, but haven't seen in a long time - will they add me or ignore me?
Thanks.