Of course it is perfectly correct in terms of grammar to speak without contractions. Here in the southern United States, however, we use contractions all the time, even in formal situations, and it would it come across as a little mechanical not to use them. Edit: Su.Ki. is right, this isn't really a regional issue. I just mention the US South because here we even use contractions that are not grammatically correct, such as "ain't" and "y'all."

It would sound very odd indeed. And the more fluent your level of English, the stranger it would seem. Words like "won't" and "don't" are essential part of the spoken language, and eliminating them would make what you say sound very unnatural. Don't forget that uncontracted forms serve a purpose. We use the uncontracted forms to add emphasis and stress particular points, so it would confuse the listener if all your auxiliary verbs were given stress. By the way, this is not a regional issue - it applies to all forms of spoken English, regardless of where the speaker is from.