Because you said this year and some posts have mentioned months that have already passed, I will tell you the best times for the remainder of the year. September and October are best. The 2 weeks after Thanksgiving are real good also. Don't go Christmas week, it is mobbed. And Labor Day weekend is out also.
If you stay at the hotels there, you can get front of the line for every ride there(only once per ride but there are employees that don't know
that). Hard Rock Hotel is the cheaper hotel at about $150 or so. If you have an ENTERTAINMENT dicount card you can get it for $20-30 cheaper. Hope this helps!