Yea avoid the Park after July 4th through the end of August. You will be looking at full queue lines for just about every ride in the park. The first 4-6 weeks of operations are the best for light crows, except for Saturday. Operations can be a little shaky the first couple weeks as the coasters need to be broken into every year after the off season, but downtime will be very minimal. May rain can creep up on the park with out notice sometimes, and we all know CP's rain policy can be frustrating, but they will have rides up and running as fast and as much as possible. Their policy is to keep rides open as much as they can. Defiantly stay in a resort if you can. They may not be High caliber resorts, but the hour extra in the morning will save you tons of time. Maverick will have the longest like ALL day, so hit it up during ERT if you stay at a resort. If you don't do ERT I usually do Maverick first thing but the line should never be longer than an hour and a half in May (Unless its Saturday).
If you come on a excellent day in may you can walk on or wait no more than 30 mins for everything and get a ton of riding in. Crews never slow their pace no matter the crowd. They will keep people moving so you don't have to wait nearly as long. Some of the hardest working crew in the amusement industry! And I don't just say that cause I am a part of it