RE: Lancast and Chester Countys.
2b pretty much covered it but I'll expand on it a bit.
The nympths to use as stated should be small,size 14 to 18,the clearer the water the smaller you go.
Egg patterns could go from 10 to 14, again the clearer the water the smaller you go.
Streamers and wooly buggers size 10 or 12 and black,white,or olive for the buggers.Streamers in various colors but something to mimick the emerald shiner is a must.
Your time period is good as the fish should be spread thru out the streams,providing there is rain as these streams rise and drop quickly.
If you can afford it a GOOD guide would be worth every penney as he will cut the learning curve way down.