Bryn Mawr proper is the providence of old money white folks who are not particularly fond of the students. That being said, housing is readily available and can be quite nice (no one lives on campus, except a few during the summer session). Apartment complexes are plentiful, cheap and mediocre. Several properties are handed down from each class to folks in the incoming year -- these are larger, group-oriented living situations. That has its downsides in terms of privacy, but you'll also be centrally located at the go-to party house, which can be fulfilling...Housing prices are reasonable, even in Bryn Mawr proper -- especially for someone coming from Berkeley.
Yes, the program is co-ed. There are more women in the postbac program than men, but it's not terribly lopsided. The undergraduate women tend to very much like having the postbac men around, though I must say, it can be a bit uncomfortable feeling as though you're crashing the "sisterhood" every day when you step on campus.
The environment is very supportive. All the little things you might have to worry about if you were doing it on your own are taken care of for you by a very talented and hard-working support staff. You're automatically registered for classes and labs, the postbac dean will liaison to any office in the college on your behalf (if you're late making a tuition payment, for instance), you'll have your own contact in the financial aid office, you'll have more TAs than you know what to do with, you'll do many a mock interview, you'll have the option to take an in-house MCAT class, you'll meet one-on-one with the dean probably more than you'd like to...etc, etc, etc.
Feel free to shoot a PM if you have any more questions -- I'll try to check this thread again soon, as well.