Now that this thread has popped back up on my radar, I feel compelled to add that ambulance girl and I did go on a second date, after which she asked to walk me to my car, then informed me that she had been seeing someone for a few months and she hoped i understood. Apparently I am really nice and smart and awesome, but she wanted to see where things went with this other girl. Whom she had been dating for three months.
I think it was questionable interest at best, so I still don't know how to tell if someone is ACTUALLY into me.