You will probably go back with the driver or tour bus you came here with, but if on the mountain without a ride back you can probably hitch a ride with one of the many daily tourbuses before noon or taxis. Check with the Club Andino Boliviano if in doubt.
Another alternative is to walk to Huayna Potosi. Bring full camping equipment and detailed maps from IGM See Maps under La Paz section. The trek is possible to do in one day with the night spent in refugio Huayna Potosi. If attemting this without gear, be sure to know the way and to be adjusted to the altitude.
