I lived in the area for a long time and JT is like my spiritual home. If your coming in on Hwy 62, stop at the Oasis of Mara and talk to the rangers and see where you can get in.(Also ask about Ranch tours) There are a couple of campgrounds within the park and not far from that entrance. If there is noting open ask about Indian Cove and it is the largest but its not in the park but between 29 Palms and the little town of Joshua Tree off Hwy 62. The park is huge but you can see it all in a day. Go in at either Joshua Tree entrance and head east or 29 Palms entrance and go west. The rangers are awesome and will tell you the must see sights. You can do it in one day or like me, spend days exploring.