Is intestinal obstruction an early symptom of colon cancer?

No. This is more commonly a late symptom of colon cancer. It is almost impossible to obstruct for right sided colon cancer. Intestinal obstruction can presnet with a changes in bowel habits or constipation.
Sometimes. Obstruction can be a sign of colon cancer, but obstruction can also occur for non-cancer reasons. A common non-cancer reason is adhesions, which are caused usually by scar tissue from previous surgery.
No. Usually this is a sign that it is a large cancer that has grown over time and is ending up blocking the colon and causing obstruction.

Related Questions

Is intestinal obstruction a symptom of colon cancer?

No. Hopefully it is more rare with good family practitioners making their patients have adequate health surveillance. Typically they are picked up with these screening endoscopies, blood in stool, weight loss etc. Occasionally you will find a stoic individual who ignores symptoms, or avoids doctors, and thus presents with obstruction instead.
All too often. It is not uncommon for colon cancers to not cause symptoms until they reach a size sufficient to block the lumen of the colon; at this point, people will typically present with cramping abdominal pain, severe bloating, and vomiting. These findings often indicate an advanced cancer that may require emergency surgery (+/-stent). The goal of screening is to find cancers before any symptoms develop.

Is constipation a sign of colon cancer? How does it cause this? Due to a bowel obstruction?

Not necessarily. Constipation is not necessarily a sign of colon cancer. Constipation is usually caused by problems with diet - not enough fiber, not enough fresh fruits/ veggies, not drinking enough water, etc. It can also be caused by low activity level. Some patients have IBS (irritable bowel syndrome) which can cause recurrent constipation. If the constipation is new with none of the above changes, see doc.

What are some symptoms of intestinal and colon cancer?

See, below. Iron deficiency anemia, weight loss, change of bowel habits, constipation, unexplained weight loss.
Colon cancer. Some of the symptoms are fatigue from blood loss and anemia, constipation if tumor advanced and causing obstruction, loss of appetite, weight loss, unexplained deep venous clots. These are some symptoms, it does not mean this all going to happen.