There are a lot of great day trips to take in the PNW, starting in the PDX area.
In my opinion, the best one for the Fiesta would be taking old Highway 30 starting in Gresham out through the Gorge, tearing up the Rowena Loops, and finishing in The Dalles. From there, you can return home on 84 if you're tired, or cross the river and head back 14, stop by Maryhill, etc. I did this in my Mustang and it was a blast. Went out 14 to Maryhill in the Fiesta but most of old 30 were still closed due to the fires.
Another great drive is starting at the St. Johns Bridge, going up Germantown, over on Skyline, then heading down Rocky Point Road. Traffic can be brutal at times, so we don't want to do this on like a Saturday afternoon, we'll for sure be stuck behind 12 Prius's along the way. There are some adjustments you can make to this course to turn it into a full day trip, but I haven't done that yet. Just the original route takes about an hour, but is action packed the whole time.
Mt. St. Helens makes for a good time as well, but the way I've done it in the past with the Mustang clubs, it wouldn't be as fun in a Fiesta as there are a lot of open roads and straights, not so much tight and technical turns. This was taking I-5 up to the Castle Rock (or something around there) exit, then heading over to the Johnston Ridge Observatory.
The Gifford Pichnot Lookout drive is maybe a better option to Mt. St. Helens. Would look something like this (disregard starting address).
Let me know if these are of any interest to you guys