Went at end of March for one week. Absolutely gorgeous/majestic sights! Living greenery at all the historic sites visited. Some say, March is the best time of year to visit for the green that you see. Weather was lovely in the 70's. Some light rain and sunny days.
We did not suffer from altitude sickness - we drank mate de coca everyday and remembered to take deep breaths frequently and kept hydrated.
Accommodations: stayed at a hostel, Piccola Locanda for the week at less than $20/night, had complimentary breakfast and internet. Excellent experience.
Tips for your trip (I wish I knew beforehand):
1) Keep your immigration stub/paperwork. You need this and passport to get home. (I say this because I almost threw my stub away)
2) Dress in layers as there may be light rain and very warm sun at some parts of the day. A light warm jacket will do. Good walking shoes are a must. Travel with a light backpack/bag that will free up your hands. There are plenty of stairs/hiking at these historic sites so this is not a destination trip for those with ambulation problems or for young children. Children, 12 and older should do fine. Bring a bottle of water with you at all times.
3) Bring crisp, untorn bills (some exchange shops do not accept the smallest tear on your bills - who knew?). Larger bills are better as the small bills do not get a good exchange rate (found this out the hard way). Exchange rate was up to 3.13 soles for one dollar -US. Betert to exchange at the main square - just get enough at the airport for the taxi.
4) Macchu Picchu - bring your passport as they have an official stamp for it. Best to get to Ollantaytambo (an hour away from the main square) for the earliest train out to Macchu Picchu. If you leave from the main square, you won't get to Macchu Picchu until noon. Unless you buy a tourist pkg, you will have to purchase your train ticket at least a day before for Macchu Picchu at the train/bus station - oh and ask for the left side (driver side) of the train for the more scenic view IF you're not going to sleep. Be prepared to spend about $70-100 for this fieldtrip (ie. taxi, train, bus, and food)
5) Food - most of the food was salty and starchy. We were craving for spice - pepper is not even offered. BIG disappointment - from the mercados/local vendors to the fine dining restaurants. No recommendations here.
6) Transportation - taxis are knowledgeable, fast and convenient and work at all hours of the night; can probably enlist a preferred taxi driver to chaffeur you for the duration of your trip). Locals travel by combis (vw vans) or buses (for longer distances) for cheap (1-3 soles) - if you don't mind the crowded/sometimes only standing room, this is the way to travel.
7) Shopping - can negotiate with local vendors, will get the best price if you hold your ground. Can wait to purchase at the end of your trip unless you go to a historic site where some things are not offered at the main square (ex. walking sticks only at Ollantaytambo, I found out too late).
8) Safety - felt relatively safe as there are a LOT of tourists, people are very helpful. There were a lot of tourist police (some who assisted in finding my lost camera in Sacsayhuaman!). Oh and don't try to take Coca leaves home - it's illegal.
9) Language - many of vendors/shop owners speak Spanish, some difference in intonation (very helpful to travel with a friend who speaks fluent Spanish like I did). Otherwise, there are a few people there that speak limited English.
10) I recommend taking a duffel bag of clothes/shoes/school supplies to donate to the poor locals (esp. Chincero). Then you can take that empty bag and fill with souveneirs home. Many locals that we met had not even been to Macchu Picchu, so please be generous. It felt great to be able to give.
LOVES: Chincero and our children guides, Macchu Picchu, Mate de coca, the colorful fabrics and local artisans work and the Quechua language/culture, spiritual healing.
If I went back to Peru, I would do the Huayna Picchu hike (light rain and paranoia made me avoid) and the Inca trail (didn't think I would make it).