You are correct that Metro is not nationwide so I can already tell that you've done some research on the subject. I'll just throw out some ideas.
From reading your post, I gathered that you probably live in the Tampa, FL market. I looked up the licenses for the Tampa market and can tell you that I would immediately narrow my search down to either Alltel, Cingular, or Verizon. If you want to use your phone freely, it sounds like you might want to get away from Sprint and leave that unfortunate situation behind you of paying for service but not being able to use the phone. I'll try to highlight the advantages and disadvantages of each provider:
Although your main concern is the deposit, without a credit history, I am afraid that you will be looking at a deposit around $100-200 with any cellular provider. You could always focus in on pre-paid plans at first to avoid the deposit though and it is refunded after one year in most cases.
Cingular: Cingular is a GSM provider so you will get a phone that can be unlocked after several months. Cingular has coverage in Tampa, New York, and Chicago. But, they are one of the more expensive providers on the market and customer service leaves a lot to be desired if any problems arise.
Verizon: I would probably recommend against Verizon. They don't use GSM phones and do not utilize SIM cards. Rates are roughly equivalent to Cingular. Verizon also locks down most of their phone's functions. Since you will utilize mp3, bluetooth, etc. you will be very frustrated with Verizon's service and how they have altered their phones.
Alltel: Probably your best CDMA choice. They don't use SIM cards so your phone would again, only be useful in the states. If you look at Alltel though, consider the Samsung U520, it sounds like the phone you described. Alltel also doesn't cripple their phones. From all I've heard, including this thread, Alltel has fantastic coverage in Tampa. Nationwide, Alltel lacks native coverage in Chicago and New York but you would be able to utilize the Sprint and Verizon networks for no extra charge on their National Freedom plan. Alltel plans also give more minutes than Verizon/Cingular and family plans are untouchable by the others also if anybody might be added onto your plan later. The family choice plan gives 1000 free texts.
I would try to decide on a carrier before focusing in on the phone though. If a SIM card is most important to you, Cingular is the clear choice, but they will also not unlock it until after you have service for several months. Cingular might also be the way to go if you want the coolest, newest phone. If you want the most minutes and the best coverage for Tampa and other places, Alltel is probably the way to go. The phone selection is probably limited to the U520, but it does appear that phone meets all of your requirements, mp3, pic, vid, bt, sd, and mobile web (Alltel calls it Axcess Web), and might save you a little $$ especially with any text messaging plan tacked on. There might be other variables, such as how will free mobile-to-mobile minutes work out with each carrier for you? How will My Circle work out for you if you look at one of those plans.
There are a lot of things to consider but for what you want, hopefully that gave you some ideas. I would just stay away from Verizon because of the crippling.
