Earlier this year I promised some notes after visiting Chaco Canyon--here is my summary. My information is based on two visits during the summer of 2013 (we drove in by toad). Others may have more thoughts to add.
Chaco Canyon is an amazing place to visit. A little extra planning and preparation is appropriate, but it is well worth the effort.
The place to start planning is the park website:
Pay particular attention to any road information on the NPS website. Some routes may be impassable at times. Consider calling ahead if there is any question.
Main entry to the park is from the north (turning off of Highway 550) or south (turning off of Highway 9). See the park website for latest directions/details. NOTE: Some maps and GPS systems still show access via Highway 57 off of 550. This access no longer exists, per the park website and latest New Mexico state maps.
The dirt roads in are rough, in places very rough. My experiences on the northern route lead me to recommend leaving your coach at a campground outside the park and driving in via toad. (I pictured every loose item in our coach ending up on the floor, and every cabinet filled with a jumble of overturned items.) Most of the folks we saw camping in the park came via pickup, van or car. During our two visits we only saw one Class A and one or two Class Cs. (A few trailers were also in the park.) We talked with one motor home owner who came in via the southern route. He said it was very slow, rough going, but his impression was that the southern entry was a little smoother than the northern route.
I would recommend carrying basic necessities in your vehicle in case of breakdown. While traffic on the northern entry is regular, it is not always frequent--you may be on your own for a while in the event of a problem. I pictured a breakdown in the evening, and a night in the desert before morning traffic picks up. Jackets, water, and maybe some sleeping bags in the trunk gives great peace of mind. Don't depend on your cellphone, signals are weak to nil on the roads in, and we had no coverage in the park. Finally, NO gas or diesel is available in the park--plan accordingly.
Once in the park, the roads are paved and driving easy. Bicycles would be great to use in the park. Many great places to see, via guided tours or on your own. Good hiking opportunities. There is a camping area. The park website gives very complete details.
We stayed in Bloomfield (north of the park) and found it a great place to base out of to explore the Chaco history. It was an easy drive down 550 to the dirt roads to Chaco. Leaving in the early morning, coming back late afternoon worked well. We had many hours in the park to explore during each visit, while still returning at a reasonable hour. Check the website for park hours.
The Chaco culture was centered in Chaco Canyon, but many smaller settlements (referred to as outliers) exist outside the park. Two worth seeing are Salmon Ruins (on the west side of Bloomfield) and Aztec Ruins (in the city of Aztec, about 9 miles north of Bloomfield). Both have been partially restored, and are good places to get a feel for the Chaco civilization. Don't worry if you see them first, they will in no way detract from what you will experience in Chaco Canyon.
Chaco Canyon is a great place to visit...Enjoy!