Yes! You can continue using your account from last year. So, for example, if you earned 2,000 XP last summer, you would still see that amount in your account (and any extra XP you earned would be added on to the 2,000).
If you would prefer to start over, you can do so by creating a new Hats & Ladders account (using a different email address). If you have any questions or issues, please reach out to the Help Desk.