I don't like my public defender and I have a pre-trial on July 29th. How can I get a new public defender?

I can't imagine that they wouldn't give you another council if you request it.

XenoSapien

It will depend, a lot on why you do not like him.
But you can request one and give the reasons

Hello c:

Fire him. Send him a letter outlining the reasons. Send a copy of your letter to the judge and send a copy to the prosecutor. Send ALL your letters certified, return receipt requested.

You'll get a new lawyer.

excon

excon's right. That's how you get a new lawyer.

Also, if you use the words "ineffective assistance of counsel", and "not concerned with the best interests of the accused" or something like that, it can't hurt.

But if you don't like him because of some physical characteristic, or the color of his shirt, the judge will not be kind, so keep that in mind.

Your lawyer works for you so it is always your prerogative to fire him/her. However, If you fire the public defender you have now, I highly doubt the court will give you another one. In that case, either be prepared to hire your own private attorney or represent yourself (which is not recommended if you needed a lawyer in the first place.)