If you cancel your individual subscription you'll still be able to post results until the end of your billed time. For example, if you had a monthly subscription and were charged on May 5, but you cancelled on May 25, you'll still have access to the site until Jun 5.
You can still log into your account and check out your results once you have cancelled your BTWB membership. You can bypass the sign up page but will not be able to log anything.
You can actually Export your results to a CSV file by logging into the site, going to your Profile Page, choosing "Workout Posts", and then using the "Export" button on this page.