When they are young it's hard to tell them apart by coloration. When you're at the lfs, try to compare the length of their dorsal fins. If some are shorter than others, chances are they are the females. Unless you plan to try to breed them, I would suggest sticking to females too. They are lovely fish and the males can get quite aggressive. The only real difference in color is that males get that red breast.
I hope this thread might help you.
http

/www.fishforums.net/index.php?/topic/72152-gourami-pearl/