My main advice is that if you really want to be hiking/camping most of the time you better narrow down the areas you want to check out. All the western states around Nevada in three weeks is nuts. You will be rushing to get to the next destination. If you really want to "see" things you want to take US highways, not interstates and travel on those roads is much much slower. I'd say do not try and cover both north AND south of Nevada. Pick ONE. If you like arid desert, go exploring Arizona, Utah and New Mexico. Maybe SoCal. If you want more mountains/forest, go north and explore NorCal, Oregon and Washington OR Wyoming and Montana (don't try to cover all five of those states!). This said, don't be afraid of long distances, just designate a day to travel fast and then once you get there take your time exploring. Aside from that;
- research things you want to see in advance. It may sound "romantic" to just go where the road takes you but once you arrive somewhere you will want to know where to go. Read the guide books and find the hiking trails that excite you.
- research stopping areas in advance. Go to the library (or a big chain bookstore; buy and return) and get as many guidebooks as you can for campgrounds. Find the ones that are free or cheap. They usually are slightly off the beaten path and you will never find them if you don't research. This link could be incredibly useful if you will be driving on US 395 in California:
Home Page - FREE Camping along HIGHWAY 395
more good links of "free" car camping:
Page Title Free Campgrounds for RVs BLM Information - blm ltva info
FREE overnight camping, state-by-state - free overnight camping, state by state
Finding places to sleep in your car - finding places to sleep in car
CHEAP places to Camp overnight - cheap places to camp overnight
Never Pay for a Place to Sleep! - never pay for a place to sleep
- that said, you should motel it every few days for your sanity. Cheap lodging is not too hard to find.
- make sure you have an extra camera with you in case one breaks.
- I do my trips solo so can't help you with the "how not to kill each other", so this may apply less to you but I'll say it anyway; books on tape are your friend. better yet, burn Steve's podcasts to cd and listen. ;p You WILL get tired of your cd's (or worse they will start skipping all the time) and there is NOTHING on the radio other than conservative Christian talk in many rural areas.
If I was in your situation here's what I'd do; I'd go with the NorCal/Oregon plan. Depending on where you are starting I'd take highway 395 through California, cut over to rte 36 at Susanville, go through Lassen's Natl Park, take the volcanic legacy scenic byway up past Mt Shasta which turns into US 97 till you turn off rte 62 in Oregon which you can take through Crater Lake NP. I'd cut over to I-5 on rte. 138 and do a "speed run" to Portland, detouring east on I-84 to check out the Columbia River Gorge and Mt Hood. Then take US-30 from Portland to the Coast, and take US 101 south through Oregon, where it becomes the Pacific Coast Highway in California. I'd probably go at least as far as San Fran, maybe LA, and then find a good place to cut back to Nevada. There is tons of camping/hiking on this route, and so much to see that you will have to pick and choose. It may not be your preferred route but it's about the length you can expect to comfortably cover in 3 weeks.
For the record, I drove from Albuquerque NM to San Fran in 11 days and that felt way too fast.