I haven't had the opportunity to travel south of Morocco, but with the help of my husband I can help you get to all the best places. If you are traveling from Spain, Italy, or France it seems the best option to Morocco would be to take a ferry to Ceuta because boats are more fun than planes, right? Otherwise, the plane is your best option.
Ceuta is a cute little city (our first vlog is filmed there) and will allow you to enter from the border to Tetouan city (where we're living now) to get you on a bus (CTM is best) to Chefchaouen "the blue city." We also have a vlog there and it's one of the most famous cities in Morocco. You must see it!
From Chefchaoun you can go see Fez by CTM bus. It's the oldest city in Morocco and I hear very often it's people's favorite to see and get an idea of the original Moroccan culture. From Fez you can go to Marrakech by train or CTM. I personally always recommend CTM bus because the train stations here don't seem organized or very safe, but it is cheaper if that's what you're looking for. Marrakech is the most visited city and has all the most beautiful hotels and spas and touristic entertainment. After Marrakech, if you have the time and ability, then go to Agadir. I would recommend it. You can see the beach! If Morocco is the last country for your trip, then Casablanca will be your last city before boarding the plane back to America. Casablanca has the famous mosque Hassan II that you can enter to see as well as an on-site museum. There's also the Morocco mall which is huge and worth seeing. Please, remember to always ask people for their suggestions on the best sights and opportunities based on the city that you're in. You never know what experiences you can discover based on good local wisdom and knowledge of the area. Always better than Google.
Other tips about traveling would be to try to see what locals are paying for things before the seller sees that you're buying something. This allows you to get an idea of the actual price so you know exactly what you should be paying and not what they tell you to pay. Like many third world countries they will charge you more for looking American and/or foreign in any way. The people of smaller/less visited cities of Morocco won't initially think you're American, but Spanish or European.
Otherwise know the dangers and safety precautions of traveling especially as a woman alone. Be mindful of your surroundings. Have access to a safe place with a lot of people or police if possible. If you can befriend a male to be your guide or something in Morocco it might save you some catcalling and unnecessary attention. Some women like to wear a head scarf "hijab" for more security from the Moroccan men that think foreign women are "easy," but you will do great traveling if you consider your safety and plan accordingly. You're a professional if you can keep safe and have fun at the same time!
Always keep a lookout for all the mosques and beautiful hidden details of Morocco. They're everywhere. Oh, one last thing. Truly be careful with eating vegetables and fruits without a removable skin, be sure all your meat is cooked through, and drink from a water bottle. I unfortunately picked up parasites here. I don't know exactly from what, but I ate from the street vendors a lot without second thought and I also drank tap water. I wasn't thinking smart I was just enjoying the new culture. It ruined my life and it's finally going away after taking medications and trying natural remedies, which is difficult to do during pregnancy. But definitely just a precaution for you to think twice before drinking and eating. A luxury we have in America is not having to think at all...Just EAT. The last point leads me to mention restaurants in Morocco...they're not always for luxury in some cities. For example, if you go to Chefchaouen and order a traditional Moroccan tajine and you see a beautiful picture on the menu, you might be surprised at the small, unsatisfying portion put in front of you. The best food is made in homes, or if you can spot a notably famous restaurant that is very busy. Some restaurants are very nice and give you that Moroccan/Aladdin feeling with lanterns, candlelight, magic carpets, and steaming hot teas. Be on the lookout for those places if you're going to spend your dirhams on eating out. Occasionally you can find a cafe that looks not so nice on the outside or inside and find yourself eating a fantastic soup, or fish, or sandwich, or pizza with a cup of hot mint tea and halwa for dessert feeling very satisfied. Try to view the meals of the people eating inside before you decide to make this or that place your final dining location and be sure to have cash on hand as credit cards are not commonly accepted for payment.
Finally...the last last last thing I will mention is the differences I have experienced from city-to-city in Morocco. In the north (where I live and see the majority of the time) the people do not see foreign people and tourists often. They stare at me, they say "hola," how are you?" "welcome to Morocco" and I can feel very foreign and in the spotlight...more foreign than usual. If I travel to a more populous/touristy area, I will blend in. The Moroccans are used to the different colors and languages of people and they will not stare at me as much, but I can still expect someone to talk to me and even my husband as they will suspect that he is European or Spanish because he's with me and because his skin is lighter in color than a lot of Moroccan people. It's not a huge issue at all, but something to prepare yourself for if you're not used to being and feeling "foreign." In summary, Morocco is beautiful. The landscape of Morocco alone is incredible with the mountain views, the opportunity to see the Mediterranean sea, and/or the Atlantic ocean, and the one-of-a-kind culture that Morocco is known for that you can see, feel, taste, and enjoy no matter where you're from. I hope you can visit and if you do, share in the comments what you liked, disliked, and whatever else you'd like to talk about in your Moroccan experience. We'd love to hear everything!