Hi Bretteee, thanks for your comment! One of the reasons why I wrote in such detail was because when I was doing research for this trip, I found a lot of the information online to be scattered and often times out of date. Hopefully this will help people who are planning their independent travel through the Altiplano. To answer your questions:
1. I was there from 3/23 - 4/8 of this year.
2. The La Paz airport tax can only be paid in cash. $25 for international departures and 15 BOB for domestic departures. There are ATMs at the airport if you don't have cash.
3. Surprisingly, a fair number of restaurants did take credit cards, especially in Chile. Less so in Bolivia. Always have cash ready.
4. Yes, all tourist-class long distance buses have bathrooms. Some routes are also run by VERY cheap local buses that don't have bathrooms, but you most likely will not be taking those. For example, the bus we were forced to take from Desaguadero to La Paz due to the strikes didn't have a bathroom.
5. Yes the altitude sickness pills work! If you have any doubts, take them. They help you acclimatize quicker. Coca leaves are more of an instant fix. They relieve nausea and headaches very fast.
If you are going from Puno to La Paz, I would highly recommend that you also do Copacabana. It was a beautiful little town, and worth the detour I think. LAN service and catering are definitely better than AA. I hope you have a great trip!