If you're driving a car you can go to Uspallata via Villavicencio, it is a very nice -gravel - road, the views (including a view of the Aconcagua) are beautiful. The road has more curves than all the roads together in the province of Buenos Aires, you'll have to drive slowly. Which is good, as you surely will see guanacos and probably cóndores too.
From Uspallata you may then go all the way up to Puente del Inca and beyond, as described above.
The Uco Valley is beautiful and there are great wines. It can be visited in a day long tour from Mendoza.
If you have time San Rafael in the south is a nice city. Other than some great wineries (notably Alfredo Roca) you can visit el cañón del Atuel a mini great canyon.
Have a ...hic...trip!