Spend 4 in Marrakech & 3 in Fez!

Casablanca - three hours to see the Hassan II mosque (you can go in)
Fez - 3 days
Marrakesh - 3-5 days
Essaouira - 2 days.
If you have more time, add on accordingly.

I don't know where you got the idea that you can't get into mosques as a non-muslim. Not sure of your gender - perhaps it's more of an issue for women. I have been in mosques all over the world. The Hassan II Mosque in Casablanca has the tallest minaret in the world and is one of the biggest mosques too. I think you need to join a guided tour there though - but it is interesting due to the amount of money and materials used to construct it.
People might avoid Casa, but it is good to see the metropolitan side of Morocco too. It's hard to advise how long to spend in each place as you may have a week in total or a month in total. Marrakech probably deserves most time.
Non-muslims cannot enter most of the mosques in any Muslim country I've ever visited, unless they are special tourist sites.

I think the # of days spent between Fes and Marrakech is the most debated subject about Morocco...some say to spend more time in Fes and other say to spend more time in Marrakech. In the end, it's your personal taste and experience that will decide. I agree with Edith too about having a rough itinerary and then seeing how it is once you get there. Sometimes that's not always possible if you have plane ticket, etc. but when you can do it, it's the best option. I usually draft up a pretty detailed itinerary and research thoroughly just so I'm familiar but almost always I stray away from it.
Happyplanet, it's unfortunate you didn't have a pleasant experience in Morocco, but I don't think it's right to put a wet blanket on someone else's plans because of your personal experience - doesn't mean the rest of us are going to experience the same. In these kinds of countries you're bound to run into problems and frustration but that's part of travelling...I highly doubt you will face less hassle in India compared to Morocco.
Your right Oceania. i am being a bit of a bast*** .
Of course, any travel exprience is good compared to ..say working day in day out. Also there are some nice things to see/experience in Morocco. There was not much to take my breath away, and I found the vast majority of people who regarded me, regarded me as a walkng ATM. They do in India too, but seem to have a culture of self pity which to me is preferable to deviousness. I've spent 10 months in India and got less aggro than the month in Morocco. Maybe its just a personal thing, I can handle Asians better, maybe i've seen too much, long in the tooth and all that.
Sorry Valenciano. Everyones experience is different. Hope yours is what you want it to be.
We're all pretty free with our opinions, and for the most part, we have no idea what the interests are of the individuals asking advice here.
I'd guess most people don't even know what kind of experience they'd like to have. Think of the difference between spending eleven days on the move around Morocco, as opposed to eleven days in one particular place. In the former, you get all the hassle that travel has to offer. In a prolonged visit to one place, you get past the hassle and have the chance to establish some genuine contacts with locals--some depth of experience.
Zooming around is fine if it's an exploratory trip in order to spend a more prolonged visit in an area that you want to check out, I'd say. I'd also say that you can also have the most remarkable, memorable experience of ANY vacation while waiting in an airport or on the plane if you luck into striking up a conversation with someone fascinating. Chance has a lot to do with the difference between a horrible and a wonderful vacation. But aside from that, you can exert a few controls on your adventure, as I've jsut suggested in the previous paragraph.
Most answers here reflect the interests of the people responding. One hates anything Moroccan, another would spend much more time in Essaouira (so would I!), etc etc. But I'm with Edith on the open itinerary. It doesn't matter. If you're one who makes a list to tick off, again, it doesn't matter what anyone says here. Just follow a guide book.
Personally, as one who's been to Morocco more often than I can remember over a span of nearly forty years, none of the places mentioned is ever on my itinerary. Except for Essaouira--which others see as a tourist trap or whatever--I can no longer stand the hassle of the Morrocan cities that seem to be on everyone's list.
Every time I go to Morocco, I divide my time between visiting my friends there and travelling to places I've never visited before--with them, or alone. Sometimes I'll just hang out in a little village somewhere. Other times I scout out a route to note places worth further exploration. Some of my time is spent hiking through the hills from one little place to the next. Sometimes I'll head off and just sit for hours in a little cafe by the sea. Or join the fishermen casting into the surf. Or I'll head off to a country market for the day. I'll rent a house and just live somewhere for a bit.
In virtually every adventure of this sort, I meet the local people, and am charmed by the generous hospitality of my country hosts. It's the much more the people, and not the places, that offer so much that we can learn from.
I'm a photographer, so maybe that makes a difference in how I approach travel. But in my case, I could spend a month just taking pictures of doors or fishboats or birds or olives or markets or anything and everything, but the real richness, as I say, comes from the interactions with the people along the way.
This ramble leads to this: what do you want to get out of your travel experience? If you're not really clear on why you're travelling, you might spend a lot of time with the logistics, and most Westerners don't do well with those in Morocco. That's why some of us advise that you simply "go with the flow." It's the best advice about travelling in Morocco that I can think of.

Nigeladvisor and others - In Morocco, you cannot enter mosques (except for Hassan II and Tin Mal) as a non-Muslim. There is debate over why - it either stems from a Maliki rule or an old French colonial one, but either way, there is no mosque tourism in Morocco.
I also know that this is untrue of other countries, as I've been in mosques in Senegal and elsewhere (Senegal is Maliki, oddly enough, which leads me to believe the Moroccan rule is colonial).

Hi and thanks again everybody for your opinions.
what I want to do is to get a feeling of the city and visit the markets.
When I began travelling, I used to do the whole landmark after landmark kind of trip, but, at the end, I felt dissapointed because it seemed as if I had visited a book rather than a country.
I know 11 nights is rather short, but all I want is to wander and experience the places rather than visiting this or that landmark. If I run into them while I'm walking the city, fine, but I don't want to feel like I'm spending my time looking for them.
I wish I could stay more time, but I don't have the money for a longer vacation. I usually try to do modest trips so that I can travel every year.
I went to Italy last year and loved it. I'd sure would like to go to India next year, but it's still too early to know.