>>1047843Crater lake is lovely, but again, going up 5000' in one go is not the wisest place to start.
Portland and Eugene are, well, cities. Here are some areas where I had nice trips when was living in Oregon:
Alsea
Cougar Reservoir
Triangle Lake
Kings Valley
Green Peter Lake
5 Rivers
I rode my bike to all of them from Corvallis, so they're probably in cycling range of you on the coast.