If no one has used your username to join the site since your account lapsed, yes, you can rejoin with your same username.
To do so, you must enter it and your old password during sign-up (as in the FAQ, Returning customer discount). The Join page will provide a suggested password but you can delete that, and enter your old one (or a new one, if you prefer).
If you participate on the boards, we’ll hold your account for you (based on your username) indefinitely.