After some digging on the Orange County Property Appraiser and the help of Google Maps, the owner of the Wet N Wild land is Southwest Land Company Inc. with a mailing address to a large office center in Newport Beach, CA c/o Mark IV Capital. The park land (or the park as a whole? Hard to tell, if anyone knows the legal history or could interpret it better than I that would be appreciated) was sold to them in 1986. They appear to be nothing more than you're average real estate development/holding company, although I can't imagine it would be prohibitively expensive to buy them out as they are very much a Southwest/West Coast centric company.
Now, in regards to purchasing land...Universal actually has no shortage of land that it owns. The only thing is that all the other land isn't exactly close to the current development, and it is in some areas broken up by other land owners or major roads. Universal City Management Properties is relatively flush with developable land if they can come up with an efficient way of getting between its largest undeveloped parcel (an approx. 580 acre plot of 3 properties, plus another 100 acres if they buy out a vacant plot of land right on Sand Lake that borders the north side of said property).
I'm still digging (I love doing this kind of stuff, you should have seen me go when the Orlando Thrill Park was announced and I had everything tracked down and connected in about two hours. I was helping a friend at Rosen write a paper on its imminent failure), but there's a lot of land and a lot of different sales and such to look at. If you're curious, I would suggest starting
here.
