FNM at grim is draft, so you don't have to worry about cards. In a draft, basically the cards are provided for you. Heres a link to how it works: http://en.wikipedia.org/wiki/Magic:_The ... ng#Limited
If you already knew what a draft was, sorry, I wasn't trying to be facetious
It's a pretty relaxed crowd at Brothers Grimm, of all ages. The magic crowd is a little older than other card games, theres rarely anyone under 15 there. Most of the people would be in the 18-23 age range and most of the rest are older with some younger. I wouldn't worry about being the 'only lady' there, there's always been at least a handful of girls when I've gone. I've seen more than ten at least once as well, some of them are regulars. On friday nights theres usually between 25 and 40 people, draft has been pretty popular lately.
If you were looking to play T2 constructed (bring your deck) that happens on Monday nights and there aren't as many people then, usually between 8 and 16. I'd start with draft, great way to get some cards for later constructed play and meet people, it's a blast. Most people are pretty humurous there, and it's not a super-serious tournament atmosphere or anything like that.
Hope this helped, and hope to see ya at Grimm.