Thanks for the invitation

I might have the tiny awful habit of complaining to select customers about my job, customers who seem reasonable enough to understand that customer service just sucks. This morning, a customer who used to work at a certain corporate earth-friendly grocery store, came in. He is about my age and we had bonded previously over the connection that he used to work with my roommates at previously mentioned store. He seemed harmless enough, and quite friendly in the beginning, but with each subsequent visit, he seemed more eager to talk to me. I've learned that it is generally a bad idea to become overly familiar with male customers because they don't seem to understand that we baristas are PAID to be nice to them. It's a part of customer service. Friendliness leads to familiarity and the idea that we are friends when, in reality, they are the customers and we are the people who serve them. There is a clear division: the counter. There are rare exceptions when a friendship is actually formed out of common interest and mutual appreciation but the rule is that we are a captive audience and just because we appear interested does not mean that we are.

I had been trying to distance myself from this specific male customer after he asked my name and appeared excited every time I took his order. Today, I cringed when he entered the cafe and attempted to take his order as brusquely as possible. He asked how my day was, I replied with my obsession at the moment--that I might die if I had to work at the cafe any longer. We complained a little about customer service and he headed toward the door. I was by the bar, talking to another barista, when he approached again. I knew exactly what he was about to ask. I hoped that he had some complaint, like all the other customers who awkwardly approach the bar area. Instead, he asked me to lunch some time. My mind raced, I stalled. What to say? The easiest would be to lie, to say that I was dating someone. But I didn't want to lie because I shouldn't have to lie. So I told him that I tried not to date customers. He mumbled that it was fair but that he didn't come in that much, anyway. I thanked him for the invitation and tried not to look at my coworker who was hiding behind the espresso machine, trying not to laugh too loudly.

I don't understand. What would ever make him think that I was interested? Is that socially acceptable? How can I prevent this?

Bottom line: I need a new job, fast. Anything might do at this point but preferably something not in customer service. Anyone?