OK, your best bet is to go to tri-met.org and look at the maps.
The Tri-Met bus mall in Portland goes right around the Greyhound depot. The 54 bus goes right by the hotel by about a block.
If you don't want to get a cab (the best idea for practicality) then I suggest you get on whichever bus leaves the stop first and take it down the few blocks to the MAX line. The tri-met stop is right behind the bus depot. Once at the MAX line you can take it East to Yamhill (just a few stops). That is the closest stop to the Hotel.
You can also just walk three blocks to the Old Town China Town stop and ride the MAX down to the Yamhill stop (only it'll be named different because you'll be westbound). That gets you just as close.
It all depends on how big.many bags you're bringing. Just a suitcase and backpack would be fine on a bus. Any more and you'd be better off getting a cab. Sinc the ride is so short you'll only be paying the minimum charge. Here's a good local taxi company.
Radio Cab