4-5 day Western US Trip in March

One thing to keep in mind in Joshua Tree is that all water must be carried. For 4-5 days you're looking at a massive load or careful planning and stashing water along the way a priori. The national forests around LA are nice that time of year (Los Padres, Angeles, Cleveland NF) and the streams might have some water. Following the Sespe River might be a nice hike

You didn't specify that you want a backpacking trip, so I assume that maybe you want to go car camping. Joshua Tree is great in the winter, although it can get cold and windy at night. You may also want to consider Death Valley which has a bit more geographical variety than Joshua Tree, with anything ranging from salt flats to snow capped mountains. Backpacking in both is primarily cross country desert hiking.

If you're looking for truly warm and backpacking, Catalina Island is an option, although it's typically a 3 day hike and you have to pay for the fairly expensive ferry. The forests around Los Angeles are nice but be careful because they definitely can be cold, snowy, icy, and treacherous at the higher elevations.

If you're looking to go a little further, Zion is beautiful in the winter, but it can get a bit chilly in the evening but nothing too bad. You can do the Trans-Zion traverse if you want a 4-5 day backpacking trip. I did it last year and it was great. Andrew Skurka has a good writeup.

Joshua Tree is one of my favorite car camping spot with great stargazing and non technical bouldering with my kids. But for out of state visitor, 1 day drive through might be enough.

Death Valley is in different league imho, offering many dayhike opportunities. Not sure of backpacking (never tried). If you have or rent 4wd (or reletively high clearance 2wd vehicle), there are so many places like remote dunes, racetrack…. and even better stargazing. (The Zabriskie point was closed recently and still might be closed though). Both parks can get chilly at night.

Joshua tree is probably 2.5-3 hrs from LA, And Death Valley 4.5 hrs.

Joshua Tree can get pretty cold in March.

Some other places to consider are:

Big Sur….lots and lots of trails here….but Sykes Hot springs is popular

Big Basin; Skyline to Sea Trail

Point Reyes National Seashore….weather can be hit or miss there, but I've spent some beautiful days there in March.

Catalina Island and the Trans-Catalina Trail.

Could also consider many of the different trips in Southern Utah or Arizona.

Big Sur, actually the Ventana Wilderness – no permits other than the California fire permit are needed. However, thanks to the drought, at any time the total fire ban (no sparking things, no cigarettes, no fires, no stoves, NO FIRE MAKING OBJECTS AT ALL) can fall down and curtail your morning hot coffee habit. There are lots of trails and then there are sort-of trails, and then there are trails on the map that are no longer there. The best place to visit to plan trips here is ventanawild.org – recent trail reports and updates there. At the moment, the trail to Sykes is closed due to a slide that happened in the last storm. All of the traffic that normally goes there (and there are many, many, many people who go there) is ending up at Pat Springs or Vicente Flat, the second and third most popular places out there. Be prepared for lots and lots and lots of poison oak, and plenty of every kind of tick (the ones that fall out of trees as well as the ones that hang out in foliage).

Big Basin; Skyline to Sea Trail – does not open until may. You can hike the trails but the trail camps close in winter.

Point Reyes National Seashore – winter is the best time to go, as this is the foggiest place on the coast. I went in January. Unless you spend the night in each designated camp you will end up with two or three days of hiking. Reservations through recreation.gov – they force you to reserve one site, pay, reserve the next site, pay…. but worth it if you can manage to get sites. Sky Camp is my favorite. Get a site on the outer loop with ocean views. The forested sites are colder.

Another option, less scenic, would be Henry W Coe State Park – probably a few weeks of hiking here, and winter is likely when the water will be present instead of reduced to small icky pools full of struggling fish. Not as scenic, plenty of poison oak, and the trails are pretty good until you are out in Orestimba Wilderness where they peter out to faint lines. Kind of expensive for parking. $5 per person per night, $8 per car per day.

Sespe (high desert) might be workable if the river is running. There are a couple of hot springs out there. Also rattlesnakes, horned toads, rabbits, bears and lions – but the bears turn tail the minute they see you and the lions we have only ever seen prints. No food storage rules, no permits, just a campfire permit if fires and stoves are allowed (this is also Los Padres NF like Ventana).

I'm a loyal Californian. But I'd be the first to tell you that, particularly in the spring, the Colorado Plateau (southern Utah, ) is orders of magnitude more interesting.

Zion, Escalante, Buckskin/Paria, Canyonlands come to mind if you're asking about backpacking. For gobsmacking views just driving around in your car, see also Bryce, Arches, Capitol Reef, etc.

Grand Canyon is king, but too late to get advance permits. You could try for a walk-in, but that may be challenging.

If she wants to see L.A., your two choices are to (a) deal with a long drive each way from L.A. to Zion (probably ~9 hours), or (b) skip Utah and see the California parks. Me, I'd say skip L.A. Fly into Las Vegas, rent a car, and see the good stuff in Utah.

– Elizabeth

Lori P makes some good suggestions. I've backpacked in Ventana and Henry Coe in March-June, and it's the perfect time assuming no major storms are passing through. Moderate temps, usually sunny, and the creeks are still flowing. Lots of poison oak too though–if she doesn't know how to spot it, it's best to avoid the coastal areas. Much worse than poison ivy. Point Reyes is nice, but can get chilly and foggy because it's surrounded by water.

Southern Utah is a strange and beautiful place. Finding water is more of a logistical issue there, but in the spring it's not too bad, and careful planning is all that is required. The potential for flash floods in the canyons needs to be taken into account too though. It might be colder there than in the coastal regions of CA, but the low humidity makes it feel much warmer than it actually is.