J-1 visa is generally issued within 30 days from the day the application is submitted. Depending upon the backlog at the American Consulate where you have submitted the application it may take up to 60 days.
Exchange visitors participating in certain types of programs may be required to return to their home countries for at least two years before they are permitted to
adjust status from J-1 visa to Green Card or apply for change of status. If not subject to the home residency requirment you may change status in the U.S.