As Mell says, work permit issues will be important to consider. Do you both have degrees? You need them to get a work permit in many places. If you don't have one, you may have to work under the table and thus need to go somewhere where this is easy. Is your TEFL course a CELTA or a Trinity course? These are the most widely accepted certificates and will open the most doors to you.
What do you want to teach? There are many options, and some countries have more of one than another. Since your girlfriend is a teacher, does she want to work in an international school or similar, teaching kids/teens? Do you want to teach children or adults? Do you want to teach in a primary/secondary school, a university or in a language school? A language school is likely to be a variety of ages and levels, and potentially some weekend/evening work. Are you OK with that?
Are you looking to make a lot of money, or just make enough to live on. Do you need to save to go traveling for the year afterwards? Different countries pay differently, and the cost of living is also a factor to take into account. One of the best countries for wages compared to cost of living in Vietnam, followed by Korea.
You say you have travelled a lot of Asia, so I'm guessing you have an idea of what countries you would like to live in. Is it Asia you are thinking of? It's one of the best places to start out in terms of money. South and Central America don't pay very well, and the Middle East is restrictive if you have no experience. You mentioned KL, but there are few TEFL opportunities there and the cost of living to wages ratio is not great. Are you looking at wanting to live in a big city like KL e.g. Taipei, Tokyo, Beijing, Bangkok, Jakarta etc, or in a smaller place. Easy access to the beach/national parks?
Do you want to get a job before you go, or sort it out when over here? Would you like your school to provide housing or are you happy finding somewhere to live yourself? Have you found TEFL.COM
and Daves ESL cafe
There are a lot of ads on there that can give you an idea of the various jobs available.
Sorry for bombarding you with questions! It will help us all to give you some good advice.
Hope this helps
[Edited: 2012 Jun 20 09:34 - Rat on the Road:23681 ]