Short Version - Being a two point hill two or more hours from Portland, Green Point Mountain doesn't get much love. But from a single trailhead you can pair it with Mount Defiance or if you want to do an overnight, three or four other hills near Lost Lake. Greenpoint has an open summit, great views north and south, and plenty of trees on which to hang a wire. ATT service is good and, like Mount Defiance, you might be able to activate it using a 2M HT with a decent antenna.
This writeup describes two approaches to Green Point: from the 411/413 trailhead (45.63657, -121.74258) that also provides access to Mount Defiance and from Rainy Lake Campground (trails 408/409). Pick your adventure: the 411 hike is shorter, steeper, and has a fair amount of tree scrambling, the 408/409 hike is a bit longer, not as steep, and requires a $10 day use pass.
Long Version - Get yourself to Dee, Oregon (45.58879, -121.62711) and Punchbowl Road, which is off Hwy 281. Follow Punchbowl to Dead Point Road. Roughly ten miles later (45.63657, -121.74258) you will see a place to park on the left and a sign for trails 413 and 411 on the right. Park here for trail 413. Note: there is room for five cars and the spots are usually filled by 1100AM. Dead Point Road is mostly Prius-friendly but has lots of twists, turns, and traffic. Be careful!
If you are doing the 408/409 trail continue on for another mile, where you see a turnoff (45.62707, -121.75746) for Rainy Lake Campground, which is managed by Lost Lake Resort. None of the usual passes work here so plan on buying a ten buck day pass, cash or check only.
Assuming you like tree scrambling (or don't like paying for a day pass) and you've chosen trail 411, you will find it about one hundred yards up the trail from the parking area. 411 bears northwest and meets trail 423 near the one mile mark. This trail isn't used much, so it is a little rough and you will encounter a fair number of downed trees; be ready to do a little scrambling. Once on 423, the trail gets better. You will head south, then west, and start a steep climb up the side of the Green Mountain ridge. There is a false summit a few hundred yards and a bit lower than the true summmit; keep going!
Choose the Rainy Lakes option if you don't like climbing over dead trees or steep climbs or both. From the parking lot (you bought a day pass, right?) head southwest on the abandoned forest road; this is trail 409. It climbs for about a mile to the junction with trail 408, take the leg that bears directly north. From here it is about a mile of gentle elevation gain to the summit, along a good trail.
In either case, you will be treated to good views of the usual volcano suspects and Rainy Lake. Be very careful, though, as the east side of the summit ridge is a precipitous and chossy cliff and a fall would be fatal. ATT cell service is good, there are lots of trees for putting up a wire, and 2M contacts are possible.