can I wait my status change from J1 to F1 into the USA?

In my opinion, you might or might not be able to be considered in legal status in the US after having filed for a timely change of status from J-1 to F-1 until the time of the adjudication. I note that your question is in one of the gray areas today since USCIS has recently begun to muddle the law in this area. Whereas it has been accepted that B visas must be maintained until the time of a change of status adjudication, that was never the case for change of status for persons holding other visa classifications. USCIS has confused the picture by putting in its form instructions for change of status that person should maintain their statuses and no longer confining the instruction to B visa holders. It remains to be seen, however, whether such a change made only through an instruction form is enforceable where the change did not come down through a properly promulgated regulation. The current form instructions state, “You must submit an application for extension of stay or change of status before your current authorized stay expires. Even if you are approved for another status in the future, you will be required to file a Form I-539 to “bridge” any gap that might arise between the expiration of your current status and validity of your future status. Therefore, we suggest you file at least 45 days before your stay expires or as soon as you determine your need to change or extend status.” Given that you have time (30 day grace period), you may consider whether it is safer to file for a change of status to B-2 to cover any gap between the end of your grace period and the date of the USCIS adjudication of your F-1 application.  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. (Sorry for the different font sizes)