Being a central Florida resident and passholder, I can tell you - don't bother going in the summer! The lines are atrocious, its hotter than hell, and by the end of the day you'll feel like cattle. My family goes all the time during the holidays. Typically, you'll run into very few tourists, and you'll walk onto every ride. Bring a jacket, it can be chilly. Also the parks really do it up for the holidays, including special discounted night hours where they have snow on main street and free Cookies and hot chocolate!
There's a lot of other things to do in the area if you are looking to save money. Check out Downtown Disney/Marketplace for free shops and eats ( I also recommend staying in a hotel there by Lake Buena Vista - they are less expensive and are connected to the Disney bus lines). Disney has 2 Water parks on property, and theres Wet & Wild closer to Seaworld. Or you could take a drive down International Drive to see lots of kitch shops and some cool places like Ripleys. Then theres always Universal.
Another great way to save money is when you book your tickets, take advantage of the meal plan. It can get very pricey to eat in the parks!
Hope this helps. :biggrin: