Hi there Trip,
Honestly, this is a hard question to answer! I am sure there are many different opinions floating around too. In my opinion, there's really not a BAD time to visit the Disneyland Resort but there are certainly months that are more favorable than others!
My personal absolute favorite time to visit is during the holiday season, and if you plan your vacation a week or two after Thanksgiving you are guaranteed lower than usual crowd levels, great weather, minimal attraction wait times, and best of all...dazzling holiday decorations and special seasonal shows and activities. I have attached a video about
Holidays at Disneyland featuring fellow panelist Ari!
In general, the least busy times to visit are the first couple weeks of December, second week of September through mid November, the first week of January through President's weekend, The week following President's weekend through mid March, and mid April through the third week of May. These are all my favorite times to visit, because you'll experience low crowd levels and beautiful southern California temperatures!
Please feel free to write back with any additional questions!
-Amanda F.