Snow is usually good in July, but South Americans have Winter vacation during this month. Resorts become more crowded, and prices are at their highest. August is usually the month with the best snow and weather. It is also less crowded than July. September usually has good snow, but conditions are sometimes spring like.
Crowds are usually small.
October is a good month for Spring skiing and riding. During an average snow year, the biggest resorts are still in full operation at the beginning of October. Instead of renting a car, I would recommend using one of the van services. But some of the smaller operations will pick you up at your hotel. When the roads are clear, it takes about an hour to get the ski areas from the city.