"Wall St" is a tremendous beast, and fortunately for you, the biggest banks have larger "IT" departments than major software companies. I put IT in quotes, because in general, I think of IT as being the networking/desktop support guys, not developers, but on Wall St, developers are considered IT. Most jobs need no real financial experience, you are just building a web app or piece of infrastructure, and in the case of real IT jobs, you are just building infrastructure like any other- a network on a trading floor might have a bit more fail over and edge protection, but its still just a network. The highest paying "quant" and automated trading jobs do require financial knowledge, but there are many jobs that don't require that.
The more dangerous question is what is the culture like? The crisis has really hit the banks hard. I used to love my job and the industry, but its really changed from work 10 hours a day because you love it and want to get ahead, to work 11 hours a day or else you are at risk of being laid off- and that risk is very real. The banks nowadays seem to hiring and firing in waves, and just kind of seeing what sticks. Layoffs are a semi-annual occurrence. I have watched the culture from generally being team based and cooperative, to very competitive. People are overworked, and no longer willing to take time and risk their projects being late to explain how something works to someone new. So in general you have to work twice as hard reverse engineering stuff and looking at years old docs and source code to learn how things work. The guys that are thriving on my team are young, single, and generally don't have friends and families in the area. They don't mind working late nights and weekends as much, and don't seem all that concerned that they are heading into their late 20s alone. I sometimes wish I never got a dog, because while my wife can tolerate me working late to some extent (because she often does as well), I have real guilt when the clock hits 7:30 pm and I know my little furball is sitting in a crate anxiously awaiting for me to come home. I also miss my wife and dog as well- it was a lot easier to work past 8pm when I only had some transient roommates at home waiting for me.
Some things that make me happy: I work on real, important systems. These make real money for the firm, and my contributions have real bottom line impact on revenue. There are no "throwaway" projects, code that doesn't make it into production, etc that I hear about in a lot of places. The pay is generally good, but as I spoke before, the hours are murderous, and bonuses are way down. They are no longer something you look forward to all year round. The culture used to be exciting and dynamic, and I hope that the industry will get its groove back, but it seems to be permanently calcified- moving from IT to the business side or to a real quantitative role is nearly impossible once you are boxed in as an "IT" guy.
Things that make me unhappy: At larger firms, its really hard to innovate. At a smaller firm, I would read about a new boost release, see something I wanted to use in it, work a little late that night to upgrade the codebase to it, and be done with it. Heard about a new IDE or compiler? I would DL it and try it out. Same for new versions of software like Chrome, firefox, or whatever. Playing with new technology makes me happy. At larger banks, everything is locked down. To upgrade from boost 1.35 to something more recent, is going to require a business sponsor, or some proven improvement- which is really hard to do when you can't even DL the source code as just about all download sites are blocked! You will be using winxp, and the approved version of the software packages your company has blessed- which is always several years behind. I was quite excited when we moved from gcc3.4 to 4.1 last year. There are lots of meetings, a lot of time spent coordinating with other teams and regions. There is also a general trend for all new hiring to occur in cheap regions like budapest, eastern europe, and India.
What I don't know, is the requirements for working overseas as a foreigner. I can tell you, that I have seen a few transfers from the US to Asia, and it seemed to go fairly smoothly. At least some of the guys I talk to in Shanghai seem to be from the US/EU, just based on their lack of accent and knowledge of US culture. I don't know for sure their background, as the time differences between NY and Asia mean its very late and very early for each of us, so there is zero chit-chat. Which brings up an interesting point- you are likely going to be in a role where there is inter-region interaction, be prepared to be on conference calls at inconvenient times.
In the US market, the best way to get a job is to talk to some recruiters- some of these guys also recruit for roles in Asia as well. Those guys are somewhat rare, but good recruiters can refer you to someone else as well.
BTW- I have been working in finance most of my career, though I did start out at a software consulting firm. Send me a PM if you want.