I've backpacked S2S variations several times and enjoyed the trip. Some tips:
- Yes, the start is higher than the end. But S2S still has long hills to climb!
- Take mosquito repellent.
- Sunscreen barely needed, you'll be hiking in deep forest most of the time, except on the Chalk Mountain variation (see below).
- Redwood Hikes makes the best maps of the area. S2S is covered by their Big Basin and Castle Rock map, revised 2013. Available at some REIs and local backpacking stores, or order online. Electronic versions available for iOS and Android. Some other maps covering all or parts of S2S are outdated or just plain wrong.
- Key water sources on S2S and variations include: Castle Rock Trail Camp, San Lorenzo River, Waterman Gap Trail Camp, Boulder Creek, Opal Creek, Big Basin Park HQ, Jay Camp, Upper West Waddell Creek, Berry Creek, and the Ranger Station/Horse Camp near Waddell Beach. Boiling, filter, or chemicals highly recommended. The official start of S2S has no water.
- The lower you go along Waddell Creek, the browner the water gets from redwood tannins, so the water tastes yucky. Much of the flow in East Waddell Creek comes from the Big Basin sewage treatment plant, so I don't get water below the confluence.
- The upper several miles of S2S are very close to noisy Highway 9. Better alternate routes are Saratoga Toll Road to Beekhuis Road Trail back up to S2S, or Saratoga Toll Road to the end and cut back up to S2S below Waterman Gap. Even better is to start at Castle Rock, maybe camp first night there, and cut over on the Travertine Springs Trail to Saratoga Toll Road.
- Waterman Gap Trail Camp is very noisy due to Highway 9. Traffic doesn't calm down until after 11 pm, with another burst when the bars close at 2 am, then commuter traffic starts by 5 am. I would skip this camp.
- Nice variation on S2S goes up Basin Trail or China Grade Road to Lane Trail Camp. No water near Lane. Continue on Johansen Road, Whitehouse Canyon Road, maybe stay at Sunset Camp, then Chalk Mountain Road, West Ridge Trail, to Twin Redwoods Camp. Awesome views from Whitehouse, Chalk Mountain, and West Ridge. Good views are scarce in these heavily forested mountains.
- Big Basin Park headquarters camp store has limited hours and a limited selection of junk food.
- Jay Camp can be a little noisy from local park traffic on weekends, usually pretty quiet on weekdays. Coin operated showers!
- Another variation on S2S is to take the Sunset Trail to Sunset Trail Camp, then hike down Berry Creek past the falls. No water at Sunset Trail Camp, Berry Creek usually has water about 1/2 mile below camp.
- A few years ago Alder Camp was closed and completely overgrown. Twin Redwoods was open. Check with the park when you make reservations. You make all campsite reservations by phone, except Castle Rock, which is first-come, first-served.
- Some campsite reservations fill up pretty far in advance during the summer. Most of the trail camps are closed November 1st through April 30th.
- I like May before the crowds get thick but the creeks are still running and the days are long; and September when the weather is pleasant. Summer can be surprisingly hot and humid in the hills, and cool and foggy near the coast.
- What Ken said: work out your shuttle. You can leave a car for several nights at Castle Rock and Waddell Beach with park permission, about 90 minute drive one-way. You can't leave a car at Saratoga Gap. You can't get from one end to the other by public transit. You could hike down and back, or hike a loop. I'm lucky, my wife drops me off and picks me up!