About thirty years ago i was on a Canadian exchange program that goes to countries all over the world. Some time after it was finished I got together with some participants from my city who had gone to other countries. There was a guy who had gone to Ecuador, a really fit strong guy, and he told us of how he had experienced really seriously altitude sickness, it had been pretty dire for him.
Your comment about going and life regrets.... Good point of view. I guess my concerns are an unknown internet person telling another unknown internet person who hasn't bike toured before to go for it, but ultimately, individual responsibility and using common sense is what matters, and your experience with the area is great perdido.
Good luck original poster, have fun getting some bike touring under your belt. It should go without saying, but get as much loaded riding up hills as you can, part of riding in mountains is being mentally ready, of course gearing and load weight are factors, but get used to riding up hills, a lot!
Cheers