I almost NEVER recommend buying/living in a trailer, unless you own the land, but in this case, I say go for it.
1) $2100 per month, not counting the mortgage interest deduction, is GREAT for the area. This assumes no residual value on the cash you're paying.
2) Getting to walk to work is awesome, worth another $5-700 per month.
3) The school situation. That's worth $200k on the price of a home. This is probably the most compelling reason to buy. Schools are a BIG deal in California.
Is this trailer new? If so, you'll take a huge hit on depreciation if you want to sell. However, after 10 years or so, the depreciation will equalize with the equity paydown on your mortgage, and you can walk away free and clear, just like rent. I think you'd do well to lock in $2100/month rent for 10 or so years. Should you want to get out early, you'll get killed by the depreciation of the mobile home.
Also, you'll need to seriously ask your SO if she's ready to be "the queen of my double wide trailer, with the polyester curtains and a redwood deck?" (Apologies to Sammy Kershaw)