Cool.
I shoot with the next version of your camera, the 400D. What kind of glass are you using? Do you have the money to drop on L-glass? I imagine so. If you have the money for the camera, and the money to do the traveling, you have $1200 to drop on a good lense. These pictures don't look like L-glass. The reason I say this is that you seem to enjoy shooting at night and in low light, and those series of lenses capture light fantastically. Often times with my lense, I really have to back down my F-stop, or else I'll be burning my censor. During the day in Djibouti I would have 1/4000 s exposures in the sun on F 4.0.
If you feel you are too slow shooting manual, then start shooting manual. Learn the camera, it's the only way to get better. You'll learn what F-stops to use in what conditions, and quickly be able to adjust your exposure lengths accordingly. It's like...when I go start shooting now, I basically already have an idea what my exif data will look like. You'll get used to the controls, which if they are like my 400D, are confusing and clumsy at first.
You like to shoot portraits, or at least people scenes. The very least you should do is set your f-stops, and let the camera decide the appropriate exposure. I shot like this for a long time, but gradually as I started getting better, I realized that I could get much better, properly exposed pictures doing it manually. But...when I am people shooting, I will keep in Av mode from time to time.
The other thing this does, is it allows you to take a swath of pictures. In some of your shots, you can't do that (mainly the good people shots, you got a blink of an eye to catch those). But in others, you could set the F-stop, and then take five shots over a range of exposures and then pick the best. I do this with my landscape shots. When I was out west shooting in the Rockies, Monument Valley, Arches, Canyonlands, there were shots that I may have taken twenty times over (and sometimes I hated them all anyway!).
But this is really the best way to get quality shots.
I completely, 100% agree with you on flash. I NEVER use flash. I hate flash. And I don't bring up my iso to compensate either. I think flash ruins pictures, whether it be studio, outdoor, night... It looks completely unatural and erases shadows. I have a friend that does interesting stuff with bounce flash, and there are some neat things you can do with it, but in general I hate it.
But in all seriousness, get out there and practice with those manual settings. You will probably be sad that you hadn't learned the skills before you went on this trip. I know I'm sad I was stubborn and didn't learn it quicker...