Abi is doing great, thanks for the good wishes.
She's a little rock star!
I'd definitely recommend sitting in on a training session before signing up and forking over money for it (I actually recommend that for any training class though). I've had really good experiences with rattlesnake training, but I've also heard some horror stories about extremely heavy-handed trainers. If a trainer won't let you watch, especially for something like rattlesnake training that requires specialized equipment that's more costly than the course itself (so it's not like you'd learn how to do it by watching and then run off to do it on your own), then that's a big red flag IMO.
I'm really a very positive trainer and I really avoid physical correction of any sort whenever possible, and I still didn't have a problem with the training I did. It wasn't fun, I will tell you that--not terrible, but normally I really enjoy training my dogs, and the rattlesnake training wasn't one of those times. But I didn't feel abusive or anything. To me, it was like a medical procedure--I've caused my dogs plenty of pain and discomfort that I'm sure they didn't understand (spay/neuter, vaccinations, removing my GSD's hind dew claws which were just connected by skin, dental cleanings, microchip insertions, etc.), but was necessary or at least advisable in the long run for the well-being of the dog. Rattlesnake training is in the same category for me--it's not something I'd ever do just for the heck of it, but if I deem the risk of a bite serious enough, it's worth it to cause my dogs temporary discomfort to protect them in the future. I hope that makes sense.
I also hope your snake season isn't too bad...I hope that for everyone, though! FWIW, I'd almost worry more about the prairie dogs than the snakes. It's a bigger concern in NM than CO (though it still happens up there), but prairie dogs are the biggest plague carriers around. Well, their fleas are to be accurate. It's not a concern for your dog, but it could be very unpleasant for you if he manages to carry a flea home, which can happen even with preventatives. It's actually not hard to catch the plague, it's just that with modern medicine you only die from it if your immune system is compromised or if you don't get treatment quickly.
I'm not doubting you at all, but I'm a little surprised that bites are common. I lived in Wellington (just north of Fort Collins) for years and was in a big rattlesnake nesting/migration/something area (I never saw so many baby rattlers in my life), and we had our dogs off leash all the time and I only heard of one bite in all that time. The dog did nearly die as venom was injected, but prompt vet treatment saved him, and I know it took them at least half an hour to get vet treatment as that was literally quickest you could get to a vet short of teleportation.
And in southern NM where I saw a freakish amount of adult rattlers and also no one fenced, supervised or leashed their dogs (ok slight exaggeration, some people had livestock fencing that snakes can get through easily), I never knew a dog to get bit. I know it happens, but I knew far more to be killed by coyotes, lost, or hit by cars than killed by snakes.
And again, I'm not trying to downplay the danger--a snakebite is definitely a serious thing, and dogs do die from them. It's just that of all the things that can happen to my dogs when we're hiking off-leash in snake country, the snakes are pretty low on my list of concerns.
Letting your dog off-leash in an open area is always dangerous, but IMO snakes get a bad rap. Or at least the western diamondbacks do, since some species are more aggressive than others to be fair.