Looking to Borrow Women's Bike

I have volunteered for the 300 mile ride this May through my employer, Harm Reduction Services. Unfortunately, I'm in way over my head, ladies and gentlemen! 

I have no former cycling experience, plus I don't own a bicycle. I know. I know. I should have thought this out more thoroughly before volunteering! But the cause (HIV/AIDS fundraiser) drew me in, and I was compelled. No choice, folks!!!

I am sincerely hoping that there is a generous and trusting member out there who is willing to loan me a bike for training and racing. I could pay you to borrow your bicycle. I just don't have the means to invest in a $1,000 + bike. Welcome to nonprofit employment!;) 

In case it matters, I don't know my frame size, but I'm 5'6".

Cheers,
Rachael R.