I am a "wild child" with the NCR and I would rather have them not shoot me on sight. I looked back at my old quests and it says I am declared a terrorist and will be shot on sight if I am inside their jurisdiction. Can I reset my infamy with the NCR in any way?
At which point of the game are you?
If you didn't get the chip back yet, try to do it (you'll have to go to NV so it may be hard). The disguise thing works, so if you have a NCR armor put it on and try to avoid officiers. When you finish the mission and have the chip, a legion and a NCR envoy will speak to you, saying all crimes against their faction will be forgotten.
And, as Aravona said, if you're playing on PC, you can modify your reputation via the console.
Else, I don't see anything possible, I would start to grieve for the clean quest panel if I were you :p.
Your negative reputation with the NCR is reset once- shortly after you meet House. Aside from the NCR and Caesar resets, there is no way to lower infamy- at least not in an unmodded game. If you're on the PC, console commands can still change rep/quest progress and mods may change this.
Wild Child reputation shouldn't be a problem however, unless you want to do the main NCR plotline. Since it's obtained by having very high amounts of both fame and infamy, it is considered neutral and shouldn't usually result in attacks on sight- even in NCR areas.
If you are considered hostile, use an NCR uniform as a disguise.