staehpj1

I really hesitate to say. I don't know you so I have no idea how you will find it, but it is a very difficult route. Youth is in your favor. The fact that you don't mind heat is too, but remember it can be extremely hot and also remember that there will often be no shade.

On the expense issue... I am not sure the coast is automatically more expensive. There is the potential to spend more on really nice restaurant meals, but that is optional. You can still buy inexpensive stuff and cook all your own meals. For camping... there also are lots of cheap hiker/biker sites on the coast. I guess you would have to add the price of a train, bus, or plane ticket though.

If you do the SC you better love to climb. There is precious little flat road on the section you propose. You are either climbing hard or descending like crazy.

If pressed to make a recommendation, I'd probably say do the coast (N to S of course), but the SC is awesome in many ways.

Cyclesafe

The Sierra Cascades south to north is doable, you just need to be prepared. Having low gearing is good, being young/fit is good; having/being both is better. Have respect for the conditions you're likely to face and you'll make it.

After the Sierra Cascades, north to south along the Pacific Coast Route will be a cake walk. When I was 53 I rode fully loaded from San Francisco to San Pedro (LA) in four days. Just so you don't think me some animal (or a liar) I have to qualify this with the disclosure that I enjoyed a very strong and sustained tail wind for most of those days.

joel2old

I will be doing something very similar to your trip at the end of August. I will be starting in Reno and go north using a lot of the SC route. Going to Crater Lake and onward to Cottage Grove before going to the coast at Reedsport(using the Smith River Rd.). Down the coast all the way to Cambria then east to Sequoia and picking up the SC route once again heading north to Yosemite and Lake Tohoe back to Reno. Can't wait to get started!

moleman76

There's a very short slightly uphill section just past Diamond Lake, but other than that it's virtually all downhill all the way to Roseburg -- 60 miles or so.
If you go west to the coast from there, you'll be south of the dramatic, rugged part of the Oregon Coast and also south of most of the idiot tourists. A fair trade. From Roseburg you can go west to Coquille and then a bit north to Coos Bay; nice park at the ocean there, sort of the southernmost part of the rocky coast.
From there south there are sections of road (101) where you will be quite a ways inland, and others where you will be on the coast.
Look for the Oregon Highway Dept's "Coast Bike Route" (name something like that) map, too.