The cycling trip south of Crescent City is thrilling and brutal. It is 80 miles to the next major towns of Eureka and Arcada. There is 4500 feet of climbing. It is tough to do in one day. Yet the scenery makes it well worth it. One should plan on camping or staying in the few (3?) motels in Klamath. If breaking this into two trips, it is far more manageable to make it to Klamath which is only 22 miles away and is only 1,400 of climbing and is all on US 101.
Instead of gutting it out all the way to Eurka, Arcata is several miles north. This still leaves 60 miles to cover with over 3,000 feet of climbing. The only way to cut this down is to camp or stay at a motel in Orick, which is not recommended.
Prairie Creek Redwoods State Park has several camping areas that are wonderful. Gold Bluffs Beach and Elk Prairie Campgrounds are popular and should be reserved during top travel months. Prior to May 15th and after September 28th, they are first come first served. Nearby are 75 miles of hiking trails, and a 19-mile bike loop. This park was used in the making of Jurassic Park.
Elk Prarie has 75 family sites and hike/bike sites and showers / restrooms. Gold Bluff has 26 tent/RV sites. Download a brochure.
Trinidad State Beach and Dry Lagoon (or Humbolt Lagoons) are day use only.
Del Norte Coast Redwoods State Park, which is a short distance south of Crescent City has 145 RV's or tents campsites. The camp is 2 miles east of the highway.
Hotels are plentify in Arcata / McKinleyville / Eureka. There are a few in Klamath. There is nothing worthwhile in between unless you are feeling adventurous.
The map below includes most of the side trips. From Crescent City to Klamath there are few options other than US101. After Klamath, there is a turn west which can be taken and is a nice break from the highway.
There is absolutely no reason to stay on US 101 when reaching the Newton B. Drury Scenic Parkway at Prarie Creek Redwoods State Park. Not only is it shorter than staying on US101, it goes through the California Redwoods.
South of the Harry A. Merlo State Recreation Area and just before crossing the bridge over Big Lagoon, there is a side trip. If tired of US 101, take this route. It is longer and further from the coast. If on this alternative, one could stay on Truck Road for a while further, but many revert to US101 and then closer to the coast on Scenic Drive. From there, it is back to the main road, then down to Clam Beach Drive which is beautiful. It is possible to skip into McKinleyville and stay at a motel there or work your way further south.