男生私下请您吃饭,量是好心,看得起您,如相互不嫌,交个普通朋友。 No big deal. One dinner in the broad daylight (even in the dark) will never put you in danger. Besides, if you are really looking for someone special, he may be a 大帅哥 with deep pocket in your dream. Do you want to miss the chance? Moreover, your posting may not only make that person feel embarrassed, but turn off any other friends-to-be as well.
Never hurt anyone in public. If you don't feel like to go, very politely apologize for your unavailability but keep your doors open.