Any idea what's wrong with my car?

I have a 95 Taurus wagon. For the past week or so, when I turn the ignition key, there is a brief rushing sound of liquid, seemingly under the hood. Nothing else unusual. At first I thought it was just rain water draining off somewhere, but today a bigger problem. Drove 20 minutes on highway to do errand, stopped and went inside, came out and big green puddle of antifreeze under car. Jiffy Lube guy next door nicely refilled. Got to garage 2 blocks away, hour before closing. They pressure checked radiator; said no leaks. Something funny is still going on. JiffyLube guy had referenced engine overheating as possible cause of overflow tube spilling antifreeze. I drove back almost entirely backroads to avoid highway, w/eye on temperature gauge to make sure didn't go past 1/2way mark. Kept speed under 50mph, mostly slower. Made it home, but now dilemma of what to do Easter Sunday...risk driving as long as it's backroads, or do I have more to worry about? Always have water jug w/me.