Hopeless Diamond
Explorer
For Canon at least, all of the EF mount lenses will work on the "Crop" bodies (such as your T3i), so if it fits a modern Canon body, it will fit your camera. The EF-S mount lenses do not work on a Full Frame body, in fact can cause damage as the mirror can hit the lens as it moves during a shot.
The Canon EF-s10-22 is considered one of the best wide angle lenses for a crop body, but you do pay for the Canon name. It's usually worth it though (at least in my mind), Canon lenses are very well made and have excellent optical properties.
What ever you decide to do/get, make sure to do it well before your trip so you can use it and get a feel for how a wide angle frames shots. Yes, you can get a lot more territory in the shot, but it also makes everything farther away. Having something in the foreground can add that dimension of scale. Up close they can (and will) add a lot of distortion, not always a bad thing and can add a different feel to a shot. Taking a lot of shots costs nothing other than disturbing a few electrons, click away and learn
The Canon EF-s10-22 is considered one of the best wide angle lenses for a crop body, but you do pay for the Canon name. It's usually worth it though (at least in my mind), Canon lenses are very well made and have excellent optical properties.
What ever you decide to do/get, make sure to do it well before your trip so you can use it and get a feel for how a wide angle frames shots. Yes, you can get a lot more territory in the shot, but it also makes everything farther away. Having something in the foreground can add that dimension of scale. Up close they can (and will) add a lot of distortion, not always a bad thing and can add a different feel to a shot. Taking a lot of shots costs nothing other than disturbing a few electrons, click away and learn