There will be nothing but hills to get to LC. Barbur is going to be your best and flattest bet. Hopping on to Terwilliger by the YMCA and heading south is a nicer ride but you'll have a steep but short start. You can also go down Macadam and cut through the cemetary (just across the street from the Sellwood bridge) but this is also going to have a big hill.
If you want to avoid the hills you can bike to Nordstrom and put your bike on the shuttle (at least they let us do that when I was going to school there) but that defeats the purpose of riding.