A friend of mine recommended this trip after she did it a couple years ago. I did the Salkantay Trail trek with a torn ACL about a month before surgery.
I was really worried about whether or not my knee could handle 4 days of mountains, but my guide was sensitive and offered alternatives that allowed me to experience the beauty of the trail even if my knee couldn't handle every element of the trail. My guide was friendly and fun and spoke English very well and was really helpful. On top of all that, the food was absolutely amazing.
My one recommendation would be to make sure you pack for a cold first couple night camping on the trail because the sleeping bags were a little on the cold side. Overall, you will be satisfied with your Salkantay adventure.