EkloNepali,

I am not sure if acceptance letter works or not

if you go for premium processing then there is chance that you get RFE(Request for evidence) issued earlier and you have to submit it to USCIS in specified period ,, if you cannot submit your I-20 then it might be a little problem. In that case if your H1B petition gets approved and request for change of staus gets denied then you have to go out of States to get stamped.

One more thing, if you are going for Premium procssing then get your I-20 ready friend,, otherwise just save $ 1000.

It's your call.

Best of luck