A little helpful advice......you may want to fill in your profile info. It helps to know what model your talking about when folks try to respond to your questions.
As far as your question, I would say it's not normal. Your car should not be that close to stalling with the a/c on. However, as DJ points out, it's normal for the rpm's to fluctuate as the compressor cycles. Does it feel really rough? Has it ever actually stalled? Perhaps your mis-interpreting the slight drop in rpm's as a near stall?