If you mean you have a DUI on your record, it depends on the conditions of probation. In all likelihood, you probably can travel as the right to travel is a strong right (unless specifically prohibited for some unusual reason).
You may want to consult with the attorney who handled this if you have been convicted.
If you just picked up the DUI and are waiting for a court date, that may be different. If you posted bail or were released OR, check those conditions first.
In addition to Mr. Mueller's sound advice, make sure to bring all court paperwork with you for your return to the US. This might come in handy if there is any confusion about the status of your case and/or probation.
There should be no issue with you traveling outside the country. Unless the judge or the terms of your probation specifically state that you are unable to leave the country than you are allowed to. As stated earlier if you are released on bail or bond check to make sure you do not violate your agreement.
Thanks for your question. A DUI will not keep you from travelling to Mexico, or, in general, re-entering the United States, unless you have as a condition of probation that you not leave the USA, or you have other immigration issues or problems.
If you are on what is called summary probation, also called court probation or informal probation, you may travel freely. Note that a few countries may not admit you with a recent DUI. Mexico will but Canada will not. If you need to go to Canada you should speak to an immigration attorney.