I was asked by one of my blog readers just about this. So I ran a poll. So far, it seems as though over 60% of those polled are taking cash only. It appears as though most cc users are charged a 2-3% for cc usage as well as a .15c fee on top of that for each transaction. Since mobile food vendors usually have smaller bills, these rates hurt them a lot.
 
Please note these fees do not include any additional cost if you rent or purchase a machine to process these bills.
 
-MC