I can't speak to inland-to-coast routes down there as we've always accessed the South Coast from Hwy. 101; so I'll leave most road recommendations to others. I've been on the Grants Pass to Gold Beach road only from Gold Beach to Agness where there was a nice RV park overlooking the Rogue River. We also drove our old Pace Arrow off that road down a county park driveway through encroaching trees and out onto a cobble rock "beach" where we overnighted all alone just feet from the river; not something I'd do in our lower-slung, taller and wider Beaver though, darn it. The road along the south river shore is not bad up to Agness, but east beyond there I'd heard not such good things. It may be better now but I would thoroughly research it first.
I'd consider 199 southwest to 101, then north to Brookings. At Rivers Edge is a nice park overlooking the Chetco, and we enjoyed a week at Harris Beach State Park north of town. I-5 to 42 is a good plan also; Coquille and Bandon are two of my favorite places. Coquille has a city or county park on the Coquille River, and there is a nice private RV park overlooking the river also that we've stayed at several times. At Gold Beach there is a large RV park sandwiched between the ocean, the mouth of the Rogue, and the little airport. A berm keeps ocean views at a minimum, but you can certainly hear and smell it. The RV park is handily central to anything there, and in season a shuttle runs you up to Jerry's jet boat venue. From there you can easily take your toad on a check-out run to Agness.
The road between Gold Beach and Port Orford goes deep into the forest to wind its way around Humbug Mountain, and it often swings high to negotiate the bluffs overlooking the sea, with spectacular views.
I am especially fond of Cape Blanco State Park, north of Port Orford. There I went walking by myself once to where the Sixes River meets the sea and had one of those special times in a life where humans are at one with nature. The tide was out and had I dared I could have walked across the river mouth on sand, but probably would have sunk irretrievably. The shore was littered with millions of shells and agates, and pelicans soared above and swam in pods in the narrow estuary. Seals fished it, occasionally surfacing to carefully examine me only yards away. A lighthouse tour and a historic farmhouse museum provide nearby entertainment, as does Port Orford a few miles south.
Bandon is a favorite of all our Coast towns, and we invariably stay at Robin's Nest RV Park off 101 south of town. It doesn't view the ocean, in fact is several blocks away, but it is easy in, easy out, has reasonable rates, is simply laid out and small as RV parks go, is well-kept and has clean facilities, and the owners were running an interesting but old rock shop when we were there last several years ago. There are viewpoints nearby along the coast, and you don't want to miss Face Rock Day Use State Park. There are several other overnight parks in and around Bandon - I'll let you research them yourself. We have stayed at Bullards Beach on the north side of the Coquille River just across the bridge north of Bandon. It is nice, as is par for most Oregon State Parks, but you'll have to drive or hike park roads or trails to the beach, as is also the norm. That said, as I recall there are a few ocean view spots along the frontage at Harris Beach, that I mentioned re. Brookings, but you may have to reserve them well in advance.
When you have more time this year, saunter farther north to Coos Bay/North Bend; many of us enjoy the Casino along the bay there. And one of the highest rated overnight locations, by Beavers or anyone else, is at Winchester Bay where the Umpqua River meets the sea, Winchester Bay RV Resort. Now you're getting into the heart of the Oregon Dunes that stretch from Bandon's famous golf courses north to the Florence area. From Winchester Bay Resort, that overlooks the tidewater, albeit not the ocean as such, you can easily explore the dunes, river, ocean, and Reedsport (where I usually fuel up at the membership-only, easy access Pacific Pride).
Medford can get pretty warm in summer, so hopefully you'll find plenty of time to hit the coast, and learn the roads and countryside. Many retire in Brookings due to the moderate weather - warm winters and summers with ocean breezes. Speaking of which, the one drawback to the south Oregon coast can be the wind, so be prepared. For me it's an opportunity to return to childhood and operate my stunt kites
. Enjoy!
-Joel