I sell internationally a lot from here in the U.S.
Frankly, there's alot of downside to accepting cash through the mail (as we call it here)... for example, he's the high bidder and supposedly send the cash and then alleges non-delivery of his item. It soon becomes a he-said-she-daid propostion and it's left to Ebay to sort it out and you wouldn't be in a very good position... how do you prove a negative as in "I never received the payment".
Secondly, f you've completed the ad and have then selected "No International Sales" you shouldn't be receiving bids and offers from international countries. I select no sales to certain restricted countries all th etime and have never received a bid or inquiry from those countries.
Last item I sold to a buyer in Sweden cost $14.00 to ship via our expedited shipping method... still takes about 7 to 10 days. (Not much help in your situation, I know). Thing is, if you advertise the mode of shipping then the completion of the shipping labelsis greatly simplified including the Declaration of Contents and your signature attesting to the fact that the item(s) are not restricted.....