Hi everyone. My visa is expired and I want to go to Mexico in order to renew it. Can anyone tell me if it's possible to come back to the states if they reject my visa. I heard you cannot come back if it's rejected. Someone with experience please share.

Why anyone needs experience to reply this and what kind of question is this?. Straight answer. If they reject your visa, you can't come back. That's all

I guess you are in F1 Visa.
you don't need to renew your visa just because your visa is expiring. If you are in status, you stay in US is legal. You don't need to renew your visa just because your visa is expiring. As long you are studying in college as a full time student or I20 is valid, you can stay here as long as you want.

 IhateAmerica, superman said his visa has already expired. 

 @ihateamerica brother ina etti saro hate yar learn to love. America lai hate garne re ani america mai ayera basne alli bhayena na ni. and one more thing bro if you dont want to answer the question then please don't but do not come here and star bashing on me. Such irony question ko straight answer cha hola tara mero lagi ali complicated cha. Timi jasto lucky, smart, good looking, handsome , buddhimani (did i say that already)  parina ma manche ali buddhu chu tei bhayera help magna ayeko.
Ya i know that i do not need a valid vis to staty in US as long as im in status. Im in status and i am going for a masters degree. I was just feeling homesick because i havent seen my parents since 08 and thats why i wanted to renew my visa in Mexico so that i could go back home for a visit. Too bad i have to wait for a couple more years at least. 
Thanks for the response brother and learn to love friend not hate on people specially Americans ;)

 jumbo/superman i think its all right to try ur luck in mexico. also canada is a good option. but if u really want to go to nepal to see ur parents why not go to nepal for a visit and apply visa from there. since u already are in the masters program it is almost certain tht u wud get a visa.