Here's a pleasant and easy pavement drive-up activation just east of Madras in Central Oregon. You might consider it as you travel between Bend and Portland sometime. There are nice views from the top, good parking, and trees and sagebrush to support most antennas. Just remember to move away from the vehicle with all your gear for the activation. 

From downtown Madras, head south on Highway 97 and turn right at SW J Street. After about 0.7 miles, this turns into SW Belmont Lane. You go another 6.5 miles to turn left on SW Mountain View Drive. (There is a gravel "short-cut" about 0.8 miles before the paved access - you choose.)  Pay no attention to signs that will lead you to Round Butte Park or anything else - that won't take you to the SOTA summit. Go about 1.4 miles south and then turn left onto an unnamed road where you'll head about 1 mile east. And then left again to go about 1.2 miles (on pavement) to the summit. 

If there's ice and snow on the summit approach road, it might be a better idea to walk up the road. Otherwise, this summit is accessible nearly year-round.