Go Sunday if you can, Saturday is going to be brutally cold.
Depending how much time you have, my advice would be to head west to Cumberland Valley limestone streams (such as Yellow Breeches) or north to the Tulpehocken. There are some good wild trout streams feeding into the Susquehanna down to your SW, and some toward Reading, but they are fairly small and going to be frozen. The area immediately around Dutch Wonderland is unfortunately a bit of a trout wasteland thanks to poor agricultural practices, at best these streams receive a single early spring trout stocking. The Conestoga can provide some bass/panfish/carp options, but I doubt it would produce in this weather, if it isn't frozen that is.
Tough time of year for that area - good luck!