Notice that you must have credits for both 8.02 and 18.03 before taking 6.002. Yes you can, but we do not encourage you to do so. Explore the wonderful activities offered by MIT, your living group, and Boston. That's the idea. The department does not expect students taking these two classes together, so they may have quizzes or major assignments due on the same day.
Some people think that it is okay to be in trouble for a couple of topics and ace the other topics.
But this is not the case. Most final exams are comprehensive and the professors expect you to be able to combine ideas and concepts from all the entire class. I am not sure what course 6 classes to take. Unfortunately there are no really easy course 6 classes. There are only hard, or very hard classes.