Well, Elrona, it depends.

Take a look at some of the Century Training schedules -- they're usually 10 week programs to get you ready for a century. Are you up to doing a schedule like this right now? Or do you need to get into shape to do the schedule?

Here's a sample schedule: http://www.diablocyclists.com/RiderT...ingProgram.htm

Are there hills on the century route? If so, you want to incorporate hill climbing into your training.

Do you want to put in the time & miles in order to get ready to ride a century? (This has been my major hurdle during the past couple of years.)

Maillotpois brings up some good points about bike handling skills and comfort with your bike on the road/with the clipless pedals. But don't despair! Are there bike clubs in your area where you could go on group rides? Anyone from your spin class who's an experienced road rider? Maybe they could take you under their wing and give you an accelerated course in road riding.

Does the ride you're considering have other mileage options? A metric century (100kms = 62 miles)? 30 miles?

I live in the SF Bay Area, and we have the infamous Cinderella Century in March. It's an all women's metric century. Several bike clubs in our area have training programs to get women ready for the ride (they teach bike handling skills as well as go on training rides.) They're generally 10 week programs, and they encourage beginners to join. The Cinderella Century is a pretty flat route. But still, it just goes to show you that you can go from being a relative newbie to riding a flat metric century in 10 weeks.

And then, you have these prodigies like TrekJeni! 'nuf said.

Good luck with your decision!

-- Melissa