My good friend... I was born in Morocco and finally went back to see it in 2000! My greatest advice to you is...be discreet, I was yelled at a few times for taking someones picture..Albeit one was of a person kneeling at prayer time. my bad!!
The markets (souks) are very densely packed and crowded so definitely go with a wide lens (18-55) will work very well. I have the 55-200 as well.. That will not suit you very well in the souks, but great to have in open spaces for those "spy" shots. I would recommend the 18-55 and if you have a prime like the 35 or 28.... Some people feel that their souls are being stolen when you photograph them so be discreet.. You will have a million photo ops!! enjoy
