jubjang,
I have done the fly-bus-ferry route to Cozumel twice now. I have used the bus both times. It typically cost $8 from the Airport to Playa, and 65 pesos for the return trip. The bus took about 45 minutes each time. There were usually movies or TV playing in the bus and that helped pass the time. There are very well air conditioned.
I believe that the vans are faster, but I can't prove it. The buses do get passed by a lot of vehicles. I doubt that the vans drive quite as slowly as the buses.
There are usually some guys on the street trying to get you to take their van for the return from the ferry pier to the Cancun Airport. We had a couple follow our group and trying to negotiate a deal with us. They almost got the price down low enough for us to bite, but that was when there were 5 or 6 of us. When there were only 2 of us once, it was not even close to being competitive on price. However, we never really did try to haggle in earnest.
I don't know if the vans are "legitimate" or not. I am sure that there are some that are established businesses, but there may also be some privateers. Enter at your own risk.
Sorry to show my ignorance, but not sure what EP is.
From what I have heard, AI is great for:
People with kids / families, especially teens that eat a TON.
Non-Diving Significant Others.
People with limited mobility.
People with limited spirit of adventure or motivation.
People with a previously destroyed sense of taste.
I have read MANY reviews on this board arguing the benefits / down sides of All Inclusive and restaurant hopping. In general, it seems like more people prefer to go eat on their own, including many that paid for All Inclusive.
I like to explore, I like to stay in town, I like to wander a bit and I have found some great restaurants. (There have been numerous threads and one recent poll about restaurants in Cozumel.) My buddy didn't like to walk as much as I do, and he is not a huge fan of Mexican food, so he was not as thrilled as I was. He had to hit MacDonald's one night (I watched, but didn't eat). To each his own.
Go with the right attitude, and have a great time!
Wristshot