Milkweed Help

[Jungletour]

I obtained one fairly large Monarch caterpillar a couple of days ago, and the
area I found it in had almost zero milkweed. The caterpillar is feeding on the
remaining milkweed which is down to about 6 leaves. It may be enough to get
this caterpillar through its final instar; however, I just noticed a second
Monarch caterpillar (tiny 1st instar) and I do not have enough milkweed for
this little critter. 

I searched the Santa Monica mountains at Temescal Canyon today and could not
find any milkweed. I need to travel in a couple of days, and I am going to
feel really bad if I let this caterpillar die because of lack of food. (Well
actually that is not an option).  

Can someone please tell me where I might find some milkweed in the West Los
Angeles area? There is an area with old train tracks that acts as a clearing
with lots of weeds. Might this be a good place? Time is ticking for this
caterpillar.

Obrigado,

Jim Hanlon