If I was charged with a minor misdemeanor offense, breach of peace, do I need a lawyer?

You should do a little of both....
Before you go to court, at least seek out and have a consultation with a couple of defense attorneys.  If you find one that you think really understands your case, see what you can do to hire them.  I'm not knocking court appointed attorneys, but more and more jurisdictions are putting caps on the funds available to any court appointed attorney for any given case.  This means that after they meet the cap, (which is minimal, at best), the attorney will no longer have an incentive (or resources) to keep working as diligently on your case.
You've been charged with a misdeanor offense. This is not a "go to the jail and throw away the key" type of case, but it can still have an impact on current and future employment options... so exploring and knowing your options is worth the current investment.  After you enter a plea, it becomes difficult (and sometime impossible) to get certain offenses off your record... even years later.
The more attorneys you visit with, the more you will learn about your jurisdiction and the nature of the judge you're in front of.  If you simply can't afford to hire one, you've at least accomplished two things: (1) you'll know how tough or light your jurisdiction is and (2) you'll be able to demonstrate to the judge that you made a good faith effort to hire an attorney.  Because of budget contraints, more and more judges are requiring defendants to seek out private attorneys before they will appoint an attorney.  Make sure you take a list of the attorneys so that you can demonstrate that you actually did talk to an attorney.  Nothing irritates a judge more than when a defendant says I talked to "atty so and so--- and she was great", only to be advised by the judge that "atty so and so" was a man... thereby catching the defendant in a lie. 
If you want to know the specific court appointment requirements prior to court, contact the coordinator for the judge or court clerk to learn what the policies are procedures are for obtaining a court appointed attorney.  This will allow you to begin working on any requirements prior to your hearing date, thereby increasing your chances of obtaining court appointed assistance.