My husband gets black unsweetened coffee at Starbucks all the time. (By all the time, I mean on the one visit every few weeks.) They are not shocked by it. I get latte, my son usually gets some oversweetened fru-fru drink.
The only problem I have with 7-11 is the fact that I leave very early for work (5:30) and at that time in the morning, the illegals have pulled up in their trucks to buy Red Bulls and pupusas (El Jefe gets coffee). I wind up being 25th in line with one guy at the register. If I want to get to work on time, my only option is to go to Starbucks.