You have nothing to fear if you live in multnomah county.
Heya, fellow Oregon grower here.
Here's the deal, the MC DA came out and said they are acting as if the law is already in effect. All currently standing cases will be dropped as long as they fall in the parameters laid out in 91. This means you can grow up to four plants out of site without worrying about state prosecution. Feds will absolutely not give a shit about four little plants, so don't worry about that. The only loophole right now is police can issue a citation for minor possession up to 500$ for under an ounce. Being a fine it would bypass the DA, and go right to collections. In other words, don't be a dick to cops and you won't have an issue. Growing falls out of that grey area, so don't worry.
Personally I live in Portland and have been growing everything for years. Hell, right now there's a few mushroom patches in my yard, a coca plant and san pedro in the window, and last year I had a ton of eight foot plants in my back yard. As long as you're polite to your neighbors no one cares.