Really, Robert W, what is your problem? You just pretty much hijacked TravelOT-Mike's thread.
Mayflower2395 was giving good and helpful information, with a link back to TA's more complete information about altitude sickness. This is completely within Trip Advisor's guidelines. There was no advertising or solicitation, just valuable information. Forum members can include tour guides or people who work for tour agencies, hotels or restaurants, as long as they aren't advertising or soliciting for business. Often, they have very good information for forum members. http://www.tripadvisor.com/help/community
And there is no limit to the number of contributions one can make to Trip Advisor forums. On some of the other forums, there are members who have made 15,000 to 20,000 posts.....
to the OP: upon your arrival in Cusco, you should just see how you are feeling & what you feel up to. With your short time in Peru, you should maximize your time in Cusco acclimatizing to altitude as much as possible. I wouldn't pre-book anything, but if you feel up to touring Cusco, Sacsayhuaman, and maybe some of the Sacred Valley, then you can book something on the spot. On the other hand, if you are feeling bad, then just rest & take it easy. Make your first hours in Cusco easy & don't stray too far from your hotel until you've been there a while to make sure you will be OK.
I don't think two days in Cusco prior to the trek has anything with getting used to the weather. It's all about getting acclimatized to altitude. The main reason people fail to complete the Inca Trail is due to altitude problems, no matter how physically fit.
But maybe you will be one of the lucky ones who has no problem with altitude! Have a great time!
Edit: just saw that the post #4 I referred to was removed before I finished typing my answer.
Edited: 11:26 pm, February 10, 2013