Buses are the best way to go from Tilcara. I had a front seat upstairs tier, and a panoramic view of the mountainous route - three hours going, three returning. All I did was step across the border and visit the market, trying to get pictures of people who didn´t want their pictures taken. Bolivians are not nearly as nice as Argentinians, much more aggressive and less friendly and cooperative. At least I can say I was in Bolivia.