mindgarden saidAh, well... the light rail won't be finished into milwaukie for a couple of more years. Dunno the current state of bike routes between there and downtown.
look into the springwater corridor, which runs through milwaukie and will spit you out a next to a bridge (Hawthorne) that will shoot you into south downtown (yep the bridge has a bike lane) --http://www.40mileloop.org/trail_springwatercorridor.htm
I think Portland's public transit is a little overrated IMO but that's just because it would only really be most useful to me on a weekend night (I'm spoiled from living in a city where public transit goes later -- in Portland it does not). There is MAX light rail, buses everywhere obviously, and a tram up to OHSU.
As far as gyms... LA Fitness, 24HR Fitness, Crunch (out east), Anytime Fitness (no idea where these area), and Eastside/Westside Athletic Club are the ones that come to mind. LAF and 24HR are especially prevalent (and basically equivalent apart from price and hours).
There's tons of hiking in Portland proper, which is really unusual. As someone mentioned, Forest Park is huge, but there's also Tryon Creek State Park which is a state park in the city boundaries. The park system here is also enormous with like 100+ city parks. They run movies/concerts/events in the parks in the summer too which can be fun.