Busiest: President s Day week � the last three weeks of March until the week after Easter � the second week of June until the third week of August � Thanksgiving weekend � the week of Christmas until just after New Years

Busy: the last two weeks of February until early March � the month of October � the week after Easter until the second week of June

Least Busy: the second week of January through the first week of February (avoiding the Martin Luther King holiday weekend in January) � the third week of August until early October � the month of November excluding Thanksgiving weekend � the week after Thanksgiving until the week of Christmas, a special time when the parks and resorts are festively decorated for the holidays

I would say that it is a waste of money to go when it is very busy.
Our favorite time has always been in the month of December before Christmas week. The weather is usually very nice and there are no lines. It is also the best time to get real deals on hotel rates.