I recently filed an I-130 for my wife and it was approved. I am a born US citizen who has never been in trouble with the law. My wife came to the US illegally when she was only 5 years old and has been here for over 20 years. She is a college graduate and has never been in trouble with the law either. My question is, how long should she expect to stay in Mexico while she waits for her visa? Also, how much should we expect to pay in Mexico for the physical exam, visa, and any other fees?
There is not enough information here. If your wife left the US less than ten years ago, she is subject to the ten year bar from the date of her departure. In order to return before she has been outside the US for ten years, she will need a waiver.
You need to retain an immigration attorney to review the case and advise you.
It sounds as if she may need a waiver for the unlawful presence which can add a few weeks to several months depending on how well the waiver packet is prepared and if additional information becomes necessary before USCIS can reach a decision. The waiver process is complicated and if not prepared correctly it can lead to considerable delays before her return. Also different consulates process these types of cases differently which could also impact the waiting times. I would strongly suggest you consult an attorney if you have not already done so to assist you in this important process.