Coolent or Airconditioner

2002 Elantra, automatic, 6 cylindar, 100000 + miles, had a leaking coolent hose replaced about a month ago. Since then when the car is started up even on a chilly morning if the air conditioner is turned on car will start up fine and about 2 miles into the trip the tempature gage will start to climb quickly above the 1/2 way mark. The airconditioner will start to blow hot air just before and during the tempature gage increasing. Turning the airconditioner off and sometimes also decellerating will drop the temp back to normal quickly. Sometimes it does not happen again during the trip sometimes it does repeatedly until parked for 20 minutes--like at the store--and then driven home 20 or more miles. Is it the airconditioner or air in the coolent system, or some other problems with the coolent system? Thank you for any help you can give me.