Overheating SL2 Problem

Hi all, my '97 SL2 has been overheating over the past 2 weeks. I was driving on the hiway at about 65, came to the exit ramp, idled at the stop light for about 45 seconds or so and the needle shot to HOT. I thought that driving it a few more blocks might cool it off, but it was stop & go traffic, unfortunately. Well, I pulled over into a commuter lot and the coolant started spewing out of the tank. Long story short, I had it towed home and started it in the driveway and within 10 minutes it began overheating..but, and here's the part I don;t like-slight water vapor was coming from the tailpipe...any suggestions? Thanks! Jay