In reply to MGA:
I've done a bit solo in Bolivia, mainly I'd try to find partners there through UKC and Supertopo, but occasionally couldn't so went off alone. Huayna Potosi is fairly simple with a motorway up and down. Condoriri (worst glacier out the lot,) and Pequenyo Alpamayo were fine with a short stretch of II/III on them. Illimani and Sajama I climbed with partners, but they would have been fine solo too.
The routes that rely on snow and ice obviously change, so they may be more or less dangerous now, the trade route is well stamped out by other parties before hand so crevasse danger is reduced. I used to wait for other parties to get an hour or two head start then follow up so they'd show the best route and fall in crevasses first!!
There are loads of local guiding companies and loads of tourists that come through, get dragged up something like Huayna Potosi to get the 6000m life tick and head on, so there is no shortage of loads of local guides that will get you up anything including Sajama at a far cheaper price than any UK guide will offer, the routes they guide on aren't that complicated, so you should be fine....