I'm surprised to say that Champaign has a fair amount of relatively authentic Mexican restaurants!
I usually do Dos Reales by myself, and I get the food to go and eat it in my hotel room. I love white cheese dip, and their's is pretty tasty. Guacamole is also good, which I get on the Chalupa. I've also tried their quesadillas, which are stuffed with fillings and white cheese dip (not flat).