I already talk with "uh" and "um" in all of my sentences. I can't talk without them. Well, I can, but if I do, hardly anyone understands what I'm saying and I often don't understand my own words.
As for public speaking itself, well, that depends on the situation and
especially my own mood. Would you ask me this two years ago, I'd say I couldn't. I just couldn't. I was too shy and too insecure to do anything like that. I forced my personality to change a lot in a short amount of time, which resulted in a very incosistent personality. Though that changes overtime.
Therefore, could I speak in 'front of a crowd' comfortably? Yes, and no, again. Another factor which plays a large role is my personal insecurity. Because of an event a long time ago, I pretty much "forgot" my real voice, therefore naturally adjusting to every situation I am in. I often noticed that when I am in front of a lot of people I am not familiar with, my voice automaticly becomes heavier, which involves me being very hard to understand. In opposite of that, when I am in front of an amount of girls I know, my voice becomes quite high and it has a very friendly tone, especially the last one according to them. There are more examples, but this all that needs to be told.
Therefore, standing in front of a crowd of unknown people, I'll probably start talking, but not many will actually understand me.
But on the other hand, when I happen to be in a (very) good mood or just in a happy state I usually am the first to stand for a crowd and start to talk about stuff. My voice becomes very understandable and the pace of my speech increases a bit. I am no longer nervous when I started and everything usually goes just fine.
But when those people are a lot older than me, I might just get some problems. Especially those around the fifty/sixty seems to get me quite stuck. Only when a lot of them are together that is.
But on a normal day, I usually avoid it. If that is not possible, I try to focus on something specific.
On a bad day, I usually get quite nervous. The biggest problem of myself is, unfortunately, I get red quite fast. Even when I'm only a bit nervous, I quickly feel the blood rising to my head. I'm more embarrassed because of that than anything else.
But as I said, I (still) have an incosistent personality though not as bad anymore as two years ago. So, it usually depends a lot on that.
If you didn't mean talking to a crowd, then it falls differently. I have no problems talking to people I know, even if I met them only once.
But I cannot start a conversation with someone I never talked to before. If we said 'Hi' to each other before, I can easily talk with that person, about... whatever comes to mind. But if that person and I never said a word against each other, I'm at a loss for words. I either need one heck of a good reason to talk to that person or... well, I can't otherwise. I noticed that a short time ago. That's why I hate calling.