Yeah, an L1 is a management transfer, and the spouse (and kids) come along on an L2, allowing them access to work and public schools, etc. I am not sure if you can file 'married jointly' from your country on an L1. You can from Canada to USA, but that may be because of tax treaty... Note, you can't file jointly on a TN, for example, or H1B from some countries.
Filing jointly for taxes is a huge benefit, as your spouse can't work until they get the work authorization, and that can take 6 months after arrival... meaning that only one of you has significant income the first year.
$120k is not a great amount of money for San Francisco. I made $125k, 10 years ago, and with a young family of 4, and 1.5 hours outside of SFO, we made it work, but there was not a lot of money left over. $2650/mo in renting a house, preschool, etc. Our savings rate was about 7% back then.
Because you seem quite flexible about living accommodation, see if your employer will provide you with a place to live for the first year, and maybe for a lesser salary. Many employers have townhomes or apartments that they keep for long term project employees, that can be reassigned to you with a bit of negotiation, and it costs them far less than it would cost you (as they have had it for many years).