tiger bro, here's another option. Find a farmacia down there that will work with you. I've been down there before for supplements and when I used the farmacia's bathroom, there were all kinds of used up needles and redijects. If you can find one you trust, he may just hold on to your bottle for you and you can just make the weekly stops. You may need to offer him some more money, but it may be worth it. For some reason I don't like the self storage idea because of the policia down there. I've heard too many stories of guys getting ratted out so that the policia can go extort some cash from you when you got the gear on you.
I live in So Cal as well and I'm heading down there tomorrow for some surfing, but much like you, I hate having to bring gear across the border. I am going to pick up some somas though, I doubt they'll haul my ass to jail for that.'