If you bump into an indigenous person, don't hesitate to communicate with them. Although they look a bit reserved at first, they open up really quickly and are great persons with even better stories though the circumstances they're living in are harsh..
Rurrenabaque is worth visiting, though many tourists have the same opinion here:D!..choose a tour which differs from the others I'd say....mostly you can have a swim in the Amazon, where Amazon dolphins are present as well!...Often each 'camp' has an own kind of pet, here it's Mr. Frederico...while we were swimming there:O!
Lake Titicaca = just awesome. If you arrive in the South of the island, just go to the North, where it's not overcrowded, and where you really experience the magical atmoshpere the island offers. If you only go to the Southern part (where really nice hotels are situated) I think you miss 80% of what it really has to offer...just a suggeston;)!
La Paz, situated between 3600 meters (Zona Sur) & 4100 meters (El Alto) is a typical South American city, at least if you look @ things like chaos, poverty, markets, and tons of traffic. Although this doesn't sound really attractive I can only recommend this epic city
Although the route to the summit is hard, there's always a more difficult one;)! If you're in the area and feel like climbing Huayna Potosi, consider the 'Ruta Francesa', where you don't walk the entire trail up, but you have to tackle a 500 meter vertical drop in the end, hard but unforgettable =)