I still have the letter and here it is ,
Coupon enclosed in your new member package will be mailed to you after registration is complete. For quicker delivery and to instantly obtain your new RapidRez number join on line at budget.com/fastbreak/delta.

Enrollment forms received via mail or fax will take up to two weeks for processing. etc...


According to the letter you get 1000 miles when you enroll and and additional 5000 miles after your first consecutive 3 day Budget rental plus a double upgrade. So you need to get your new RapidRez number prior to renting in order to get this bonus.