You could always do what my friend does when we go from Brawl to Melee.
When he plugs in the controller he holds the analog stick slightly down (and I do mean very slightly).
When the analog stick is in neutral position, it will treat it as if it is always slightly down. If you hold it down too much every jab will just be a Dtilt, and if you don't hold it down enough it won't have the tap jump "off" effect.
There's kind of a magic middle position where it won't register a neutral position as down, but it won't register an up press as a hard press up. So essentially you don't jump when you hit up, because the game thinks you are slightly pushing up, and tap jump is "off." IMO its just too much trouble to bother with when you could just learn to play without tap jump...
That's all I can say if you don't want to go out and get an Action Replay