To add to what was previously said, there are a lot of great trainings available online.
More specifically, you can look at Udemy courses. By taking one or two short courses before you go to take a degree, you will be able to further validate if this is the right career for you. 3 or 4-year degree commitment is a lot in case you are not sure if this is the right thing for you.
There is another great training you can look at here:
The only program I know of personally (and I haven't taken it) is called "The Guild Hall"
I've worked with a few designers that graduated from there, and I've also worked with a few teachers that used to teach there. So I know they are a good school just from working with those people.
The reason I have, most likely, is because it's located in Texas. (I'm in Texas)
But since you're in San Francisco I'm sure there are equivalent schools there if you chose to find something closer to you.
I know Gnomon is also an excellent school and have a couple friends that have taught there:
I'm not sure of the costs for either school, but I imagine they aren't cheap. So if you are financially unable to go there, you might want to look around for a community college class that is taught by someone in the industry. Make sure it's taught by someone currently working at a game studio. And the reason I say this is you will not only learn from someone who is currently working at a studio, but you'll also have a contact (a way in) that will help you find your first job.
Valve is very close to you as well. Send them an email. Let them know what you want to do and see if you can talk to someone who can give you some tips.
I'd also recommend downloading Unreal, it's free and you can start designing levels right now.
Who knows maybe you'll make some awesome levels and get a job without having to go to school :)
Good luck and I'll see you on the other side.