Google:
Clackamas: Bonnie Lure Park, Eagle Creek, Eagle Fern Park, Cross Park, Barton, Bowling Alley Hole, Milo McIver Park(probably late summers here)
Sandy: Dodge Park, Cedar Creek, Lewis and Clark etc.
Better yet, spend some money and get a map(if you want to do your own scouting) or hire a guide to save your future unnecessary expenses for products that are -most of the time- nothing but shiny, glittery, feathery magical things that catches fishermen more than fish! A good guide will put you in the right direction on what to use where...
Map is from Amato publishings and called Oregon Rivers. There is also a book that talks about all Oregon streams and lakes, and suggests tackle to use for each location. I don't remember what it's called now, but they have updates -I believe- almost every year to the book.
Good luck...