Haasmukh bro, Once you leave the country, your university will issue a new I20 and you need a new F1 visa to re-entered. I am not sure whether it is worth trying to get the visa from either canada or mexico, since you are almost there to obtain your diploma. but WHAT IF they denied you to re-enter in the US, then you will be middle of NOWHERE. Better you talked with your International Academic Advisor, they have better idea about these stuff and what is the denial rate from that University. So best of luck bro