Dave if you are looking for a warm place in Jan. Joshua Tree is not it. You are talking high desert in winter. Temps at night go below freezing. The closest motel is about 30 miles from where they will be. Hence Sharon and I will stay in Palm Springs.
Palm Springs is the closest but there are at least five different areas in the park that have infrequent plane landings & takeoffs. Course if you use them you do attract the attention of park police. (if seen)
Lots of small fields/strips in the area used by some when they don't want to be noticed.. if you are flying your own or a small plane.
Having grown up in the town of Joshua Tree and wandering all over the area I was suprised to hear of these landing strips. My grandfather was a ranger there and I don't remember ever hearing him mention any landing stips in the park. And thinking about the topography there are only a few places that one could land. The Pinto Basin, The upper Covington Flat area, and some back roads on the way to Cotton Wood. There is a dry lake between JT and 29 Palms but there is an airstip right off the main road. Even closer would be the TINY 29 palms airport and 20miles away the TINY Yucca Valley airport. You still need a car once you get there. I would love to know where these 5 places are, not because I have any intention of flying in, but the geography is such a personal interest to me.
The weather in that area is very hard to predict in the fall and winter. In early Feb. 03 it was 85 and sunny. Last year for the JT workshop it was down right cold and windy (That is what I remember most about winters as a kid). Two weeks ago my parents called me to say that there was 8 inches of snow @ 5:30 in the morning, and 11 inches @ 2 PM. I wish I could have been there, but they soon closed the two northern roads into the park.
Aggie, I would not sugest staying in Palm Springs. With the "Low Desert" sprall getting worse it will take you more than an hour and half to get the workshop. And that is the Short way. There are three major motels in 29 Palms and those are only 20 min max from Jumbo Rock campground. Not to mention it is only about a 10 degree temperature difference from Joshua Tree. Not exactly sun bathing weather (unless you hail from Iceland).
I wish I could get out there for this year's workshop. Last year a handful of people from the workshop came to my house to look at photographs, have coffee and talk before going home to catch the tail-end of the super bowl. Air-fare being only $200 from Philly it might be possible if I can get the time off.