Go for computer vision/pattern recognition. There seems to be a shortage of enough 'good' people for them - even in HN I read very low quality vision related blog news as if they are very good ones... (I remember an image rotation article a few months back...). There are very good CS guys here but vision/learning seems to be a bit underrepresented...

I'm getting pretty good contracts for doing research work from pretty big US companies/startups and I'm not even located in US...

I did electronics engineering in undergrad, signal processing in masters and computer vision in phd - also took some courses in physics. I sort of wish I did some formal math courses (optimization/graph theory/variational calculus) as well. Applied math will help you a lot in CV/ML domain so that's a pretty good idea for you to get it. ML is very hot and there are lots of people going after that but don't forget to check out the geometric part of the cv - finding camera calibrations, stereo, multiview stereo or the realtime stuff as cv is being used more and more in mobile apps... Computational photography is my new focus these days - I'm getting more queries about that... PM me if you like more detailed info...