Any suggests for lens for canon rebel XT for Africa? Do you really need mutiple lens? Or is there one lens that can do it all?

"do it all" is a pretty big order. You have to think about what you are trying to get pictures of. Some distant leopard from a mile away? Or an ant crawling at your feet? Or a really wide angle scenic shot? No lens does it all.

A canon 28-300 L would do pretty well for everything but the wide angle stuff. It is about 2 grand though. Another 600-700 for a wide angle (got to be super wide for the rebel due to the cropped sensor) or you can use the kit lens (I do).

One of the big reasons you got a DSLR was that it allowed you to change lenses so you can use something that is designed to do a particular job (telephoto, wide, macro) vastly better than the ultrazooms. You can go the one lens route but you will be disappointed somewhere.

Go to photo.net and search the discussion posts. This sort of thing gets asked (and debated) alot.

Tamron has an 18-250 that might be a good all-rounder. Of course, if you get it dusty or break it you are screwed.

I went to Tanzania recently w/ 30D 70-200f2.8L, kit lens that was a 17-85 IS, 2x converter. A big kit, for sure, but worth the extra effort to lug around. Got some excellent images that turned out to be the highlight of the safari. Dr.C

Me personaly if I was going to africa I would bring multiple lenses.
I would have the 70-200 L USM IS 2.8. The L series is good quality glass from ziess. IS is a image stablizer which is very handy if hand holding this very long heavy lens, but it would do better on a tripod. The 2.8 aperature would also be a must for me because how fast it is and great it is in low light.
I would then bring along a 180mm macro for the upclose still life and small wild life or insects.
Then I would bring a good quality small zoom lens. I personaly own 17-85mm L 4-5.6. It takes very nice pictures.
I would also have a back up camera and tonnes of cards and a pelican to pack my gear in.
As stated above these lenses are very expensive.
70-200 L IS 2.8 is around $2000.00
Macro $1000
17-85 L 4-5.6 $500-600 new. If you have a camera shop near by that sells used I would bring my camera down and start pricing out used and trying them on my camera for accuracy and weight. Make sure there is no scratches on the surface or dust inside the lens. Zooms are more prone for dust.
Good luck. Africa would be awesome for taking pictures.