Guys, could you please share your experience on that? I have one question, my visa got expired(F1) , the passport is still valid though. Got i-797 approval notice with me. I know, if I go to Canada and Mexico, I can come back within 30 days. But if  I dont get my PP stamped. Will they allow me to enter US again? Wont they check the visa on the border. I'm bit confused. I'll be really grateful if someone can share.