My advice would be to go to EZE instead.

I don't think you're going to find any "nice" hotels, nice food or nice anything, really, other than the scenery. If you can take a train to La Paz, do so (I took one from EZE and don't even know if there is one from Santa Cruz). The train travels on the altiplano and all of a sudden there is a gorge with La Paz below - a truly spectacular sight, especially at night. Ruins of Tihuanaco nearby. Also, if there is time, Lake Titicaca would be in order. I have been there (La Paz) once and it is one of the few places I really don't care to return to. Dress warmly.