I would be extremely surprised if a judge allowed an attorney to withdraw from a case the day before trial unless that attorney was able to secure you a continuance. If you can no longer afford an attorney, you should ask the court to appoint the Public Defender's office. Good luck.
If your case is in Miami-Dade County State Court then the Judge will very likely continue your case and allow the attorney to withdraw.
If your case is in the Southern District of Florida Federal Court then the Judge almost certainly not allow the attorney to withdraw and will proceed with the trial.