Still working on it.
Thanks for all the input. Frankly, I was so fed up yesterday that I didn't even fool with it, but today I'm headed home to double check all you've said before heading back to the shop Monday.
-I don't think there was anything wrong visually with coolant and shop made no mention of seeing anything wrong with it.
-car can idle forever without overheating!
-no matter what, the TOP hose is HOT, and the BOTTOM one is cold.
-148,000 miles, timing belt has been replaced, not sure about water pump.
-Had already mentioned the heater core possibly being blocked and, for whatever reason, mechanic didn't think it was that.
-Will definitely go home and carefully see if i can see coolant flowing through radiator!! I really get the feeling its not and definitely overheats that quickly under load.
Thanks for all the ideas!!.....starting to see a little ray of hope its not the HG. :)