The Northern California Fly Fishing Board

I agree - Sims,

or Castle Crags park, just south of Dunsmuir

or splurge and try the Cold Creek Inn in Mt Shasta - pretty good rates the last time I was there.

The other thing, is that a lot of that area is National Forest. Most places in National Forest, you can camp anywhere you want. Sims is pretty primitive, but it does have water and toilets. Castle Crags is some better, as I recall. The Forest has trees, and you might be able to get away from the train. It can be loud in Sims.

Best of luck!