Hi Nick--
I commute past that complex a lot. Very pretty! I feel your pain on the cost of living. As I see it, you have two options that would work. 1) take a look at craigslist. There are a couple whisper rooms up for sale, or have been lately. Around $2k and under, IIRC. There's also a guy in Santa Rosa that advertises on CL his "soundbooths unlimited" products, at about $500. They look like acoustic foam and acoustic blankets adhered to the plastic that anvil cases are covered in, then all hung from tubing. I have no experience with them, but they might work.
Option 2 is to take a look at Soundwave Studios...they have a rehearsal complex off Grand Ave/880, just a few miles to your building. Not the best option, but you should be able to pick up a roomshare for around $200-300 that might work for you. Again, craigslist.org under the 'musicians' section is going to be your best option for getting into SW on the cheap. No fun to commute to practice, but hey, the neighbors ain't gonna complain.
Option 2.5: if you don't need to be in that complex, take a look at Alameda, it's got a lot houses with cottages in the back yards, is very safe, good public transit to SF, not terribly expensive.