If you are prone to motion sickness, take an extra pack of Dramamine.  The ones they sell down there are harder to swallow because they aren't enteric-coated (rough when you already feel yucky).  A prescribed patch behind the ear (like when you are going on a cruise) may be an ideal solution.

San Martin de Los Andes and Bariloche are beautiful and Mother Nature is awesome, however... manual transmission transportation, scenic driving on ripio (pebbled) roads, high altitude, meal time changes, boat rides on not always smooth lakes, too much yummy chocolate and few restrooms make for a ghastly combo.