Early December can be a great time to visit, although the weather can be iffy in terms of temps. We've been there at that time with gorgeous 70-degree weather and another occasion with temps barely reaching the 50's. Crowds are average; I think more folks realize it can be a good time to go if you want to avoid crowds and/or hot weather. Some rehabs take place then. You won't have the parks to yourselves, but it's not bad, IMHO.