A/C does not stay cold after coming to a stop

When I turn on the A/C in my vehicle, the engine performance almost bottoms out. It feels like it is bogged down and sluggish. When I am going constant (the interstate), the A/C works well, for the most part. If I come to a stop though, the air stops being cold, becomes warm air, and the engine does not idle right. A mechanic friend of mine said that he thinks it could be the A/C compressor failing. I have had the Freon checked and recharged, but I am still getting progressively worse performance. Could it be the compressor? I know that, in smaller engines, the A/C will cause some drag. But should the air not also stay cool when you come to a stop? Any suggestions would be greatly appreciated.