To be valid, the Waiver of Citation must do all of the following:
1. Be signed by Respondent, in front of a notary, after the Petition has been filed.

2. Expressly state that the Respondent waives his or her right to service, and has received a copy of the Petition.

3. Be filed with the clerk's office.

4. Include the Respondent's address.
If you're asking whether you can get your ex- to agree to sign and get the form back within a week, that's not something we can know. Have you asked him?