You can register for attendance of GRADES2017 via the SIGMOD registration site.
The price for attending GRADES is $180 with various discounts ($150 for ACM/SIGMOD members and even $100 for student members -- $150 for other students).
The deadline for early registration is April 7. If you register after this date, the prices will be higher (resp. $200, $250, $150 and $180).