A few photo suggestions in the Teton:
*Oxbow Bend
*Down Antelope Flats Road (I think that's the name) to the Moulton Barn. Any photo that includes the Moulton Barn will be a winner! This is also a good spot to photograph bison up close.
*String Lake.
*Inspiration Point.

maj,

Changing lenses on-the-fly takes practice.

Essentially, you're trying to hold a camera that is open to dust & dirt, hold a lens that has just been removed and hold another lens that will be connected to the camera.

Each lens has a back cover to keep it clean.

Managing this takes practice.

= = = = =
Wow!!! A 70-500 with a 2x.

Who makes that? Does it have Image Stabilization?

What kind of image quality do you get?

Do you PP your images?

It must be a monster. Not something you carry on a trail.

Your Xsi just came out. Good buy!!!

I'm now 2 generations back with my 350xt. But mine has more experience at well over 12,000 shots.

We change our lenses frequently, but are usually doing it by the car. Mike has a pouch type thing slung over his shoulder (he made it to fit his needs) where he can easily get to a lens and put it back while changing the other on trails.(and uses his pockets also) But, admittedly he also has me to hold one if he needs me to. We frequently just keep the camera attached to a tripod in the car while travelling about for easy access because it does take time to attach it.

We have a Sigma 170-500mm (about 4-5lbs) and a separate 2x teleconverter (I think it is a Canon). They don't recommend using a teleconverter with a 500mm lens because you do lose picture quality.
It does not have image stabilization, but on our last trip he was shooting mostly in RAW (for the first time)and manually focusing. He said the farther out you go the harder it is to focus. And heat waves are a problem at times out there, no matter what your lens. He is just beginning to fool around with the editing. We've always had it, but didn't use it much before. Also, this trip was definitely a learning curve with both the camera and lens. And no we probably wouldn't take it on a long trail -- although people do. The fun part is trying to get all this into your carryon when you are flying.

Long story about the XSI. Basically it wasn't supposed to be out in our area until after our trip, but they sent 2 cameras to a number of stores right before we left and we ended up getting it at Best Buy.

Know what you mean about your 350xt. I've seen some of your pictures and they are great. I love my (old by today's standard) camcorder -- it has done me well.

Have a great trip!

Sadly, we only saw the SIGNS for animals when we were out last year! We were out in late March/early April on a road trip that spanned several states, but saw absolutely nothing wildlife-y in Wyoming ... unless you count the buffalo herd that are permanent residents of Hot Springs State Park in Thermop. Sad, really, since it took us till Idaho to even see a deer! By that point, we'd been on the road about four days already.

Your trip sounds wonderful, though. Intrepid Best Friend and I are planning a tentative road trip to Yellowstone this summer since we missed it last year. But first, we have to get through our week in the Big Apple and see if we survive.