As Blue Lizzard says it is a fab day out, but be careful which one you book, because a few years ago I went on one in Oludenez, and we were told that we would stop on the way back while they washed the jeeps down, and we got back after 8pm! a really long day, although a lot of fun! Just make sure you take lots of sun cream and wear a hat as you can get really sunburnt.
J