Joshua Tree and Anza Borrego are close enough to do both during the same day, but we would have to sacrifice some of the southern part of the drive to make it work. Something like the 78 through Ramona and Jullian, then once in Borrego Springs you'd take the Borrego Salton Sea Way to the 86, take that up through Mecca. In Mecca Box Canyon takes you right to the southern Enterance to Joshua Tree.
It would look a little something like this:
http://maps.google.com/maps?f=d&hl=en&geocode=408662626620589604,33.109701,-117.054620%3B11286535026845182117,33.135680,-116.379960%3B721783223554448860,33.256880,-116.343850%3B12523735997323735767,33.569321,-116.080819&saddr=San+Pasqual+Valley+Rd+%4033.109701,+-117.054620&daddr=CA-78+%4033.135680,+-116.379960+to

alm+Canyon+Dr+%4033.256880,+-116.343850+to:66th+Ave+%4033.569321,+-116.080819+to:33.680925,-115.804138&mra=mi&mrcr=3&mrsp=4&sz=11&sll=33.724911,-115.751266&sspn=0.343225,0.748444&ie=UTF8&ll=33.630057,-116.020432&spn=0.343604,0.748444&z=11
Again we should do this SOON!!!! Like next weekend. Borrego is in full bloom right now!
http://www.parks.ca.gov/?page_id=24977
The mouth of Coyote Canyon at the end of DiGiorgio Road is blanketed with a gorgeous combination of verbena, phacelia, lupine, popcorn flower, filaree, brown-eyed primrose, chicory and desert dandelions. All of these flowers can be seen just off the main road up to Desert Gardens. These flowers are still abundant
but some species are fading. It is still very beautiful.
http://www.nps.gov/jotr/planyourvisit/blooms.htm
Wildflowers may begin blooming in the lower elevations of the Pinto Basin and along the park’s south boundary in February and at higher elevations in March and April. Desert regions above 5,000 feet may have plants blooming as late as June.