The housing market around Caltech is normally expensive (136% the national average) but good quality housing for students and post-docs is available with a bit of looking.
Most people I knew found that walking around near campus and finding phone numbers on posted signs was the most expeditious way to find a place. Let's face it, in this market, the good and affordable rental properties don't need to waste money on advertising because hanging out a small sign generates more than enough phone calls.
California State Code §702.13 "All citizens must obtain a California State Driver's License and be able to parallel park a Cadillac Seville."
Just kidding but this is California and life here without an automobile is restricted. It can be done, but you'll be relying more on your friends to get around.
The lab has a collection of old written driving exams. A bit of study of these will often allow people from states other than California to pass the written test. Otherwise, reading the booklet helps ;->
Surprisingly, many people from foreign countries have trouble with the practical exam, particularly if one takes it at the office in Pasadena. Rumor has it that the examiners there may be a bit tougher (at least as of October, 2000).
Peter N. Steinmetz