What does the cafe setting of Sure Thing suggest about the characters? David Ives originally planned to set Sure Thing at a bus stop.

There are a variety of different things a reader or audience member can infer about the characters based on whether they meet at a bus stop or at a cafe.

Cafes attract a certain type of customer, stereotypically.  When one thinks of a coffee shop, one usually pictures younger people, college students, professors, poets in berets, drinking coffee and having poetry readings.  It an environment for people reading books, having intellectual conversations, and working on laptops.  It's a place where people go to meet other people for a quick date or meeting.

Conversely, a bus stop serves a more utilitarian purpose.  People often are at bus stops together against their will, and it attracts a more random section of the populations.  Also, people spend less time at a bus stop--usually less than 15 minutes, depending on the bus schedule.  That gives people less time to talk and interact.

People who have chosen to be at a cafe would tend to be more relaxed and have a purpose for being there rather than people at a bus stop who are forced to be there for a shorter period of time.