Hey WanderingJim,
I've taken the Shepherd Pass Trail a few times and I really enjoy it for the experience of climbing out of the desert right up into the alpine environment. Starting as low as it does and with a first night at just 10,000' (Anvil Camp) I think helped me a lot with acclimatizing. The times I've done it have been in September when all that was needed to beat the heat was an early start.
I did have car trouble one time but that was my fault. I ran over a large loose rock. That road should normally be passable for any kind of car with appropriate care.
By-the-way, the Salkantay trek is amazing.
