Johnny Manziel says there will be no raging bachelor party in Vegas -- or anywhere else for that matter -- before he gets married ... because he's dead serious about returning to the NFL.

We got Manziel leaving Delilah in WeHo ... he tells us his wedding to Bre Tiesi will probably go down next year, but he's not down with a bachelor party. Hard to tell if his boys are cool with that or not, though.

As we've been reporting for months ... Johnny insists he's a changed man and left his partying past behind to get himself back to being a world-class athlete.

We've seen Manziel out a lot lately, and he's been in great spirits and always seems totally sober. Sources close to him tell us he's focused on training every day ... which he confirms with us.

As for the NFL ... Johhny gives mad props to Myles Garrett, who just went #1 in the draft to his former team -- the Cleveland Browns.

He thinks he'll do wonders for 'em ... we all know they need it.