Hey Rachel,
First of all... I'm no expert. 'Kay?
It might be easiest if you look for either Chair Yoga or Adaptive Yoga. I think they both fall under the umbrella of Hatha yoga, the kind I practice. I'm AB and haven't done any but I know that my instructor offers Chair Yoga classes. Those are poses that use a chair. I think that she uses folding chairs, but the main thing is that I think it doesn't require time on the floor. Hatha yoga uses blocks and other props to help us attain alignment in the poses. It's about breathing and alignment, mostly, and I think that in Chair Yoga the chair is just another prop.
Here are some links that offer info about Chair Yoga.
http://www.ehow.com/how_2047781_do-chair-yoga.htmlhttp://en.wikipedia.org/wiki/Chair_Yogahttp://www.yogainchairs.com/default.aspAnother thing you might look for is an Adaptive Yoga class. I recently read
Matthew Sanford's book Waking. He's a pioneer in the field of Adaptive Yoga.
I offer that because those instructors should be somewhat knowledgeable. If that's not what you're looking for then I think any instructor worth his/her salt would be able to involve you. Mine is constantly paying attention to her students and watching for things going on with us anyway. I attend a level two class (which is more advanced than Ms. Rosa's level one and less than her level three, heh

) and I can see how some of the poses we do could be modified. As a matter of fact, it's all about modification one way or another. Using blocks if your hamstrings are too tight, or the wall for balance.
The main thing is to find an instructor who listens to you and always remember that yoga is about the connection between YOUR mind and body. My instructor reminds us constantly to "go only as far as the body allows you." I hope you find what you're looking for and that this helps.
Namaste