If it was written by a native English speaker, it would read:
To Tan Yi Du
C/O Ren Cao Tang Wan Cao Tang
From Li Kong Hu
But I want to make out the literal translation, keeping the flavour of the language in which it was written. I think I am satisfied with the following:
Lucky letter, pray it finds revered honourable Uncle Ren Cao Tang Wan Cao Tang
Pass on to Tan Yi Du
Paid for and sent by Li Kong Hu from San Francisco
Thanks to everyone for your comments, particularly lungao for helping me clarify the Ren Cao Tang Wan Cao Tang part (one and the same!). I don't see that there is a direct reference to a transfer of earnings. Wells Fargo also delivered mail in this period so I have to make the assumption that this was just a letter.
I am curious as to why you think the sender was a woman. The Victoria on the right was "via Victoria" as in the letter was sent by way of the city of Victoria. Doesn't the name Kong Hu sound more like a man's name? Also, doesn't the handwriting look more like that of a man? I know in English, one can usually tell the gender of an individual by looking at the handwriting.
Anyway thanks again!