So should you use note cards to deliver a speech? Yes, you absolutely should! Your audience doesn't reward you for memorizing things. Here's what I would recommend, though. Boil it down to one note card or, what I do is I take a regular 8.5 by 11 sheet of paper and just narrow it down. I actually cut it out, so I end up with something no greater than this.
Now, the reason I say note card and not note cards is if you're having to shuffle cards, that's distracting. It typically means you haven't done a good enough job of really refining, editing, and narrowing your message down. If you've done your job, you should have narrowed your speech down to about a handful of key, important points. And then you need a few words to remind you of a story for that point, maybe a bullet point or two for a key fact or number. Maybe something to remind you of the slide, if you're using PowerPoint.
But if you're giving a speech of an hour or less, you really shouldn't need more than a single sheet of paper or one large note card. I caution you against numerous note cards because they get out of order, they fall down, and you need to have bigger print so that you can glance at it without having to pick it up or fumbling around and doing all this stuff. Make your font large enough so that you don't have to put on glasses, you don't have to pick it up. Here's the key with notes: it's fine to use them, but if you have your notes limited to a single sheet of paper or a single note card, and you have it sitting flat on a lectern, on a table, next to a glass of water, you can move around, gesture, talk to people.
They will think that you're just talking to them and that you're not using notes. So your audience will perceive you as incredibly confident, authoritative, and comfortable. Personally, I always use notes. Any time I'm giving a key note speech, and I speak at least 100 times a year. But here's the key, my audience never has any idea I'm using notes. They never see my notes. Why? Because I have it on a single sheet of paper, large font. I never touch the notes. I never pick it up. Because it's one page, they never see me turning pages, so it creates the illusion of mastery. So yes, use your notes.