@shl Perhaps you could use the "Phrases" feature to modify the text that reads: "After registration you will receive an email confirmation with a link to set a new password" on the sign-up page. 

I use the WordPress login page along with another plugin to modify that page, so I'm not sure of other ways to modify the WPForo signup page. Maybe someone else could help you more, but yeah, using the Phrases to change that message to something that suits you might do for you.

@shl,

changing the message text from phrases is the proper way to do that.

Many thanks @Chris @realact - phrases worked for us!