There are two ways you can opt your client out of Porch, without disabling the Porch connection entirely.
From the Client Edit Screen
In your ISN navigate to Clients/Agents -- Clients -- Clients
Then, find the client you'd like to opt out and click the pencil icon to the left of their name.
Check the box 'Do not send any emails or SMS messages relating to Porch'
Then hit Save Client and you're all set!
From the Order Form
When editing your order, navigate to the section where you enter client data and check the box for their record titled: 'Do not send any emails or SMS messages relating to Porch'.
Continue working in, and save your order as normal.
Be sure to save your order after marking that checkbox, and the client will never be contacted by Porch