I agree with Baja on #1, but he is way better at the Euphorbias than I am. #2 is a cylindropuntia, could be C. californica, as that occurs there I think. #3 definitely an Opuntia, but I think the pads are wrong for phaeacantha.
#4 an Euphorbia, I have seen a picture of that one somewhere recently but cannot remember the name.
