[CommandoDecoy]

Does anyone know the order in which the cities are unlocked in the game?

The city is Liberty City with a chain of islands (7 in total and one of which you cannot gain access to; that I know of). The islands range from Firefly Island all the way to Happiness Island. At the start of the game you have access to at least three islands Firefly, Charge, and Bohan (they never named this island). I would assume that once you complete enough missions on Firefly Island then you would gain access to Colony Island and Algonquin Island (another one they never named). I know that the ending cut scene takes you to Happiness Island because of reviews.

I hope this helps and this is not official, I am just taking a guess since I am still on the starting three islands.