I'm in the slightly embarrassing position of not knowing any more vocabulary than "no habla espanol", but that's not normally a problem in fast food restaurants, where you can order meals by pointing and sign language and usually get more or less what you asked for.
But for some reason here in Spain I just can't get my head around what country I'm in. I find myself automatically saying "hai" for yes, or "bitte" for please, and I think I lapsed into French today too. Although I'm wearing my "I Am From Space" T-shirt, so people probably expect a language barrier.
Incidentally, that shirt gets more comments and laughs from people on the street than everything else I own put together. I need to wear it more often.