For such a scenic, enjoyable National Park, relatively few crazyguy riders seem to have written about Joshua Tree. Here are a few thoughts about J Tree for anyone who might consider riding there.

When to go

Cold nights in the winter. Hot days in the summer. I judged April the best chance to encounter moderate conditions, although you never know for sure, especially when it comes to the wind. Check online weather sites for average temperature measurements. Avoid spring break. Shoot for the middle of the week to minimize competition for campsites, because weekends can be crowded with climbers and other folks. No hiker/biker sites.

How to get there

From the south, the intersection of Interstate 10 and the road to Cottonwood Spring is the only option. That road north from I10 is known variously as Cottonwood Springs Road, El Dorado Mine Road, and Pinto Basin Road. At that exit from I10, there are no services whatsoever. Just a dusty intersection.

From the north, you can turn south off Highway 62 at Twentynine Palms or the town of Joshua Tree. Both of those towns have full services. Entering from either town puts you on the park's main loop.
As of spring 2013, fee is $5.00 for a bicycle to enter the park.

Roads

Entering from the north, you'll be on Loop Road, which runs through the park in a semi-circle between Twentynine Palms and the town of Joshua Tree. (Outside the park, Highway 62 is the direct route between those two towns.) Loop Road intersects the road to Cottonwood Spring. All paved. Not much shoulder anywhere, but not much traffic. Other than Loop Road and the road to Cottonwood Spring, not much pavement in the park. A few unpaved, four-wheel drive tracks. Also some hiking/equestrian trails. Bikes allowed on any road where vehicles can go, but not on trails. Note: Spring and summer of 2013, heavy-duty road construction underway between Cottonwood and Loop Road; it's a mess right now, but the road should be smooth and wide by fall 2013.

From the town of Joshua Tree in the north to the intersection with I10 in the south is about 62 miles. Riding from north to south means over 3700 feet of climbing. Riding from south to north means a little over 4800 feet of climbing.

Camping

Multiple campgrounds in the northern part of the park. Only Cottonwood Spring in the south. Depending on the campground, sites are either $10 per night or $15 per night. No hiker/biker sites or overflow camping. Except for Cottonwood, none of the campgrounds have water or electricity. (Black Rock campground also has water and electricity, but it's in a separate corner, not connected to the remainder of the park by road.)

Back-country camping is free, but must be located at least one mile from the road. That's probably a deal-breaker for touring cyclists, unless you want to sleep closer to a road and take a chance on being rousted by a Ranger.

Motels

The Joshua Tree Inn (also known as the Cosmic American Experience) isn't the only nearby option. At least one other (nicer) place in the town of Joshua Tree (very close to that park entrance), plenty of places in Twentynine Palms (very close to that park entrance), and more places in Yucca Valley (which is about six miles from the visitor center in Joshua Tree). No lodging near the south entrance.

Water

Not many sources in the park. Water is available at the Oasis Visitor Center (in town of Twentynine Palms), Black Rock campground (isolated from the main part of the park), Indian Cove Ranger Station (another isolated piece not connected to the remainder of the park by road), West Entrance (on the road about five miles south of town of Joshua Tree), and Cottonwood campground (at the south edge of the park). Basically, unless you can "borrow" water from other campers, you can only replenish H20 at the northern or southern boundary of the park. That means you'll need to plan carefully and carry supplies accordingly, especially in the summer.

Depending on who you listen to, "experts" recommend one or two gallons of water per person per day for traveling through the desert. I carried roughly a gallon per day in relatively cool weather and didn't run dry, but I paid attention and didn't waste a drop.

Electricity

I'm a little hazy on this, but I think none of the campgrounds where I stayed had electricity. Saw outdoor electrical outlets at Joshua Tree visitor center and Cottonwood visitor center. Maybe outlet at the Cottonwood amphitheater where the Rangers give presentations; that's right beside Cottonwood campground.

WiFi and cell signal

No wifi in the park. I could get a cell signal up to a couple miles south of the Joshua Tree entrance station, but nowhere else within the park.

Gear

Bring a light. At night, pit toilets can be very dark and spooky.
Except Cottonwood (3000 ft), the campgrounds are at 3800 feet or higher. Even on warm days, the desert can chill down considerably overnight. Be prepared with suitable sleeping bag and/or clothes.
The National Park website states "Food-storage containers capable of preventing access by wildlife are required," but I never saw any raiding critters at Belle, Cottonwood, or Jumbo Rocks.

Tips

The distance from the north edge of the park to the south edge is only about fifty miles (about sixty miles if you measure all the way from town of Joshua Tree to I10), so it can be pedaled in a single bound. However, that probably won't leave much time for enjoying the place. Unless you intend to just blitz through the park like any other piece of road, plan to spend some time hiking and exploring the joshua trees, cacti, and rock formations. Tons of photo opportunities.

If you plan to camp, bring cash. Unlike Death Valley—which has high-tech, automated credit card kiosks—Joshua Tree campgrounds still use the old-fashioned method: Put your cash in an envelope and put the envelope in the iron ranger.

If you're entering from the town of Joshua Tree, you can wait and fill your water containers at the entrance station, which saves lugging it about five miles uphill.

Remember, there are two distinct deserts inside the park limits. The high elevation Mojave desert covers the north and west with fantastic rock formations and joshua trees. The low elevation Colorado desert (part of the larger Sonoran desert) covers the south and east with a much more barren landscape. 

Resources

Be sure to take a look at the official Joshua Tree National Park website:
http://www.nps.gov/jotr/

And here's the park map:

http://www.nps.gov/jotr/planyourvisit/upload/jotrmap.pdf

Journals

Here are a few journals I've identified with information about J Tree:

American Redemption 
by Jeff Arnim
https://www.crazyguyonabike.com/doc/page/?page_id=317432

Temporary Tuaregs 
by Scott Wayland
https://www.crazyguyonabike.com/doc/page/?page_id=101345

Long Haul Truckin' 
by Matt Cazales
https://www.crazyguyonabike.com/doc/page/?page_id=95208

Tour de Jabantik 2006 
by Allen Ho
https://www.crazyguyonabike.com/doc/page/?page_id=35180

Finally

Treat the park with respect. Already too many signs of graffiti and vandalism. Recent news articles indicate some parts of the park have been closed to visitors due to damage. Please do your part to help protect this beautiful natural treasure.

Have fun and ride safe.

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