I'd love mounts. As long as they are not too fast, nor to slow, too strong, nor too weak. And not too cartoonish either. For a bear, you could have constructed a harness for it with a seat on the top to so you don't have to worry about the width of the animal and the leaning forward. I'd still like horses though, and/or donkeys. I think they work perfectly in an post-apoc, and I don't see why they should be extinct, they haven't been mentioned There are many animals that aren't mentioned, are they extinct too? Cazadors weren't mentioned till they showed up in the latest game. And I'm not happy with the answer from the Fallout bible:
1) Did horses (in any form) survive the Great War, within the area of California? Arguably, I imagine that if they did, horses would begin to replace cars as the main mode of distance transportation.
Nope. Some mules did (the poor mule killed by the raiders in F1), but not for long. Besides, I think that mule was a discrepancy.
Although, the question was just about within the area of California. And why would mules outlive horses? They are sterile. I bet there are loads of horses somewhere.