my i20 is expired. Can i apply for visitor visa?

F-1 student status has 60 days grace period under which you are considered legal in the country. During that period of time, you can apply for a change of status. If you wish to apply for visitor visa status, you would fill out form I-539 with appropriate fee and assurances that you will leave the US at the end of your requested period of stay.Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.  

If your student status has expired, you are required to leave the US.  You would have had to change to visitor status while you were still in student status to avoid leaving.  From outside the US, you can apply for a visitor visa and return using that visa.