Can I leave my luggage at the garden while visiting? If not, would I be allowed to take a suitcase inside?
I'm afraid that, as of December 2015, the only public luggage lockers in the city Marrakech can be found:
- At the ONCF railway station, according to this Routard thread (in French)
- At the Supratours bus station, according to this Voyage Forum thread (in French)
- At the Gare Routière (bus station) at Bab Doukkala, ibid.
- At the CTM bus station, according to this Yahoo answers thread (in French)
The other option is to ask your hotel to keep your luggage after you check-in. If you are planning on visiting the Jardin before checking-in I will also suggest that you show up to your hotel and ask them to store the luggage for you.
Now I don't know if you can enter the Jardin with a suitcase. You can always try.