It's not so much the individual parks, although some you just don't bother to try, but you just have to be careful with individual sites. Trees are our biggest issue with the slides, and sometimes the site we picked may not be the one we end up with.
Unless you have a tight spot that is your all time favorite, you can overcome the opposing slide space pretty easy. It's no more of an issue than awning placement, steps, cord length, hose length, and all the other things that sometimes work against you when setting up.