A withheld judgment is a two step process. You ask for it when you are sentenced and you ask for it again, via a motion, affidavit, and order after you have completed probation. You must have a probation violation free term of probation to successfully get the withheld judgment. Until you have taken the second step in the process, you are considered convicted of the crime under Idaho law. Additionally, even with a withheld judgment, the DUI can always be used to enhance any subsequent DUI.
You should always defer to the advise of your attorney, especially if they practice in the geographic area and area of law for which you sought their advice. However, you may need to seek additional advice, or we need additional information to more acurately answer your question. According to the Florida Stautes, if you plead no contest, or guilty to a DUI in Florida, there is a mandatory adjudication of guilt. I am not aware of any way to have adjudication with held if you are convicted of a DUI in the State of Florida.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. Laws vary widely from state to state. You should rely only on the advice given to you during a personal consultation by a local attorney who is thoroughly familiar with state laws and the area of practice in which your concern lies.