My former co-worker would say Laotian.
To OP, we went to Peru this past October, so, same time frame you are considering. We went on our own, no
ABD. However, we took almost the exact same itinerary as ABD does.
In regards to the altitude, neither of us had any issues. I purposely planned our trip to work from the lower altitudes, and up, which I believe ABD does as well. So, we did an overnight in Lima, straight to Sacred Valley (Ollantaytambo), MP, Cuzco, back to Lima.
Even doing this with no guides, we experienced nothing whatsoever that had us in fear. Local Peruvians were generally very helpful.
Overall, we absolutely loved Peru. The food, the culture, the people. Everything. The only thing that hesitates my want to return, the bug bites I received at MP. While they don't affect most the way I was, I'm in no hurry to return. Itchy bites for 8 WEEKS!! Needed steroidal cream for them.
Tourist wise, I think there were mostly people from other South American countries, and Europe.
I would highly recommend that time of year to visit. While the bug bites have me in no hurry to return, I do not regret going one bit. MP is truly beautiful. You think it looks good in photos, there are no words I could use to describe it in person. Breathtaking. After my trip, and posting photos on my fb page, Peru has moved up on my friends lists if places to visit. Do not miss the opportunity.
PS. I am on my phone, so I cannot see where you are from. But, travelzoo had a deal on airfare. R/T from LAX was $269 including fees. Yes, $269!! Deals were available from other cities as well, and only covered fall dates.
Enjoy whichever you decide!! Cheers!!