Collegiate racing is awesome and a great way to get started.

There are lots of juniors races of all age groups around here, and the junior women usually race with the boys, but it can vary greatly. Do some research on your local races to see what you'd be in for there. If you wait till next season, then you'll be racing as 18, so it won't matter. You'd be in the women's 4. So also be on the lookout for what types of women's fields are in your area too. Are there many 4 fields or do they tend to be open (1/2/3/4)? Jumping into a race with some super fast ladies can be really intimidating, and if that's your only option, I'd cast my vote for going to a college with a racing club instead.

Try www.bikereg.com and search your geographic region.