Noah's ark is where all of the "locals" go because it is frankly the best outdoor waterpark.  There are lots of ways to get discounts.  They have some on their website.  My kids went for free when the had "A" report card days.  In June there are lots of "Free" days.  I have a LOT of kids and my 17 year old took them.  They only had to pay to park ($10).  She took 7 of them there and didn't pay any admission as they all had at least one "A" on their report cards. 

Chula is ok, but it is better for little kids.  Most of their water amusements are for little kids.  Wilderness and Kahlahari we feel are much better during the winter season.  They have large indoor areas that are geared to all ages.  Mt. Olympus grew out of what was Family Land and Treasure Island and a few other smaller water parks.  All of them were cheaper alternatives to Noah's Ark, which has always been the largest.

If you go I suggest going on a Tuesday to Thursday range.  Those are the slowest days and they have the most discounts.